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The contributions of domain-general and numerical factors to third-grade arithmetic skills and mathematical learning disability
Get PDFExplanations of the marked individual differences in elementary school mathematical achievement and mathematical learning disability (MLD or dyscalculia) have involved domain-general factors (working memory, reasoning, processing speed and oral language) and numerical factors that include single-digit processing efficiency and multi-digit skills such as number system knowledge and estimation. This study of third graders (N = 258) finds both domain-general and numerical factors contribute independently to explaining variation in three significant arithmetic skills: basic calculation fluency, written multi-digit computation, and arithmetic word problems. Estimation accuracy and number system knowledge show the strongest associations with every skill and their contributions are both independent of each other and other factors. Different domain-general factors independently account for variation in each skill. Numeral comparison, a single digit processing skill, uniquely accounts for variation in basic calculation. Subsamples of children with MLD (at or below 10th percentile, n = 29) are compared with low achievement (LA, 11th to 25th percentiles, n = 42) and typical achievement (above 25th percentile, n = 187). Examination of these and subsets with persistent difficulties supports a multiple deficits view of number difficulties: most children with number difficulties exhibit deficits in both domain-general and numerical factors. The only factor deficit common to all persistent MLD children is in multi-digit skills. These findings indicate that many factors matter but multi-digit skills matter most in third grade mathematical achievement
Pressure-activated, colour-changing and flexible material for aiding lymphedema patients in performing the MLD massage: An explorative design study
No full textThe MLD massage is a key component of a lymphedema patient’s treatment. Currently, research is ongoing manifesting a transition from system care to self-care by designing robotic sleeves that are able to perform an effective and safe MLD massage enabling the patient to gain a sense of empowerment and ownership over their treatment and time. This research presents an innovative approach towards the MLD treatment by introducing an intermediate step: the bio-inspired design of the patient training education tool (PTET), a tool which aids the patient in performing the MLD massage safely and efficiently by themselves. The PTET is a pliable and slim sheet that easily adapts to the contours of the limb. Exerting manual pressure onto this sheet induces a colour change at a specific pressure threshold, giving the lymphedema patients a visual sign they have reached the required amount of pressure for this type of massage. The mechanism of colour change is inspired by the cephalopod’s dispersion and aggregation of its chromatophores. This study presents the design and validation of the working mechanism of a bio-inspired flexible colour-changing sheet, and first insights into the adaptability of the design variables and their relation to the threshold pressure, threshold indent and degree of colour change.Mechanical Engineering | BioMechanical Engineering | BioInspired Technolog
Controlled release from protein particles encapsulated by molecular layer deposition
No full textMolecular layer deposition (MLD) was used to coat micron-sized protein particles in a fluidized bed reactor. Our results show that the dissolution rate of particles coated via MLD rapidly decreases with the increase in number of coating cycles, while the uncoated particles dissolve instantaneously.Chemical EmgineeringApplied Science
Analysis on Governing Processes of Mixed Layer Depth Variability in the Labrador Sea
No full textAs a key component to the bottom limb of the Atlantic Meridional Overturning Circulation (AMOC), the Labrador Sea is one of the regions where deep ocean convection takes place. This convection is driven by atmospheric cooling during winter, which brings the surface water into the intermediate and deep layers by uniformizing water mass properties. This homogeneous layer is called Mixed Layer (ML). As a result of this convection, stratification is no longer maintained, and the Mixed Layer Depth (MLD) deepens. During this deepening, an enormous amount of potential energy is converted to kinetic energy, and meso- and sub-mesoscale instabilities develop. After wintertime, the MLD starts to shallow again. Atmospheric-induced convection ceases or decreases significantly and physical components return to stratified conditions. Baroclinic instabilities grown to mesoscale or geostrophic scale play a role in restratifying the ML through the formation of coherent ocean eddies. This chain of processes follows a seasonal cycle that strongly depends on the imbalance between horizontal and vertical buoyancy gradients. A practical way to quantify this imbalance is the use of the Ertel potential vorticity or a derived magnitude as the Richardson angle, which allow to infer the existence of instabilities and to classify them respectively.This study analyzes the physical processes behind the MLD seasonal variability in the Labrador Sea. To this end, high-resolution model data (1/12° × 1/12°) from a global simulation has been used. An evaluation of spatial and temporal patterns of the MLD and energy conversion is provided, and the dominant types of instabilities are determined. It is hypothesized that these instabilities drive the energy conversion and the growth of coherent mesoscale eddies, which can modify the MLD and restratify the ocean. Finally, the sequential interactions among the processes are investigated to provide better understanding about seasonal MLD variability. This study shows that the density-based MLDs with a threshold of 0.03 kg m^-3 are the most credible values, and the spatial and temporal patterns of energy conversion and gravitational/symmetric instabilities are in phase with the MLD variability. The energy conversion is investigated by means of the available potential energy (APE), kinetic energy (KE) and Energy Ratio (ER) which is introduced in this study, and a large amount of gravitational and/or symmetric instabilities is found within ML, especially in the upper ocean layers. The role of baroclinic instabilities is investigated with the Eady growth rate, while the presence of coherent mesoscale eddies is inferred from the Okubo-Weiss parameter and the Eddy Kinetic Energy, whose size is limited by the internal Rossby radius. This study shows that the MLD variability is the result of changes in the conversion between the available potential energy (APE) and kinetic energy (KE) as well as of the competition between ravitational/symmetric and baroclinic instabilities. The former favoring MLD deepening, and the latter favoring MLD shallowing.Civil Engineerin
Model Predictive Path Planning of AGVs: Mixed Logical Dynamical Formulation and Distributed Coordination
No full textMost of the existing path planning methods of automated guided vehicles (AGVs) are static. This paper proposes a new methodology for the path planning of a fleet of AGVs to improve the flexibility, robustness, and scalability of the AGV system. We mathematically describe the transport process as a dynamical system using an ad hoc mixed logical dynamical (MLD) model. Based on our MLD model, model predictive control is proposed to determine the collision paths dynamically, and the corresponding optimization problem is formulated as 0-1 integer linear programming. An alternating direction method of multipliers (ADMM)-based decomposition technique is then developed to coordinate the AGVs and reduce the computational burden, aiming for real-time decisions. The proposed methodology is tested on industrial scenarios, and results from numerical experiments show that the proposed method can obtain high transport productivity of the multi-AGV system at a low computational burden and deal with uncertainties resulting from the industrial environment.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
Atomic and Molecular Layer Deposition for Controlled Drug Delivery
No full textThe majority of pharmaceutical products is made of solid powders. The morphology and surface characteristics of drug particles affect both their bulk behaviour, e.g., flowability, dispersibility and tabletability, in the manufacturing process of dosage forms as well as their bioavailability upon administration into the human body. For instance, in pulmonary drug delivery, particles with an aerodynamic diameter <5 µm are required to reach the action sites of the lungs. Surface modification provides the means to tailor crucial functionalities of pharmaceutical particles, such as dissolution, wettability, flowability and dispersibility, based on the desired formulation design. Atomic layer deposition (ALD) and molecular layer deposition (MLD) are gas-phase film technologies that enable atomic-level control over surface properties through the fabrication of nanoscale films on individual particles, which impact the powder performance. The benefits of ALD and MLD for pharmaceuticals compared to existing surface modification techniques include (i) gas-phase and fully solventless nature of the process, (ii) wide range of process conditions, including low temperature and atmospheric pressure, (iii) control over the amount of deposited material and film thickness in the sub-nanometer and low-nanometer range, (iv) high drug loadings due to the nanoscale films, (v) uniform and conformal films, crucial for tailored functional properties. Moreover, the possibility to carry out ALD and MLD in fluidized bed reactors offers scalable processing and manufacturing of bulk quantities of nano-engineered powders, relevant for pharmaceutical applications. This thesis deals with the development of ALD and MLD processes on excipient and drug particles, especially for pulmonary delivery, to control their release and enhance their dispersibility and flowability.ChemE/Product and Process Engineerin
Estimation of mixed-layer depth from surface parameters
Get PDFAuthor Posting. © Sears Foundation for Marine Research, 2006. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 64 (2006): 745-758, doi:10.1357/002224006779367285.Mixed layer depth (MLD) is an important oceanographic parameter. However, the lack of direct observations of MLD hampers both specification and investigation of its spatial and temporal variability. An important alternative to direct observation would be the ability to estimate MLD from surface parameters easily available from satellites. In this study, we demonstrate estimation of MLD using Artificial Neural Network methods and surface meteorology from a surface mooring in the Arabian Sea. The estimated MLD had a root mean square error of 7.36 m and a coefficient of determination (R2) of 0.94. About 67% (91%) of the estimates lie within ± 5 m (± 10 m) of the MLD determined from temperature sensors on the mooring
Smart release of corrosion inhibitors by a novel encapsulation method
No full textThe objective of this project is to explore the feasibility of atomic layer deposition (ALD) and molecular layer deposition (MLD) as methods for the encapsulation of corrosion inhibitor. It is desirable to encapsulate the inhibitors before incorporation into the coating in order to provide a smart release only at specific conditions (acidic and alkaline pH in this case). ALD and MLD are processes to deposit conformal thin films with atomic and molecular level control, which leads to excellent step coverage and conformal deposition on complex micro- and nano-encapsulate structures. In this project, ALD and MLD process in different conditions were applied to three environmentally friendly inhibitors, namely 2-mercaptobenzothiazole (2-MBT), Ce(NO3)3 and Li2CO3, which present high protection performance against corrosion of aluminum alloys. After MLD and ALD, coverage of the coatings were characterized by scanning electron microscopy (SEM), coupled with energy dispersive x-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Leaching of coated inhibitors in solutions was studied by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ultraviolet-visible spectroscopy (UV-vis). Finally, the encapsulated inhibitors were incorporated into epoxy coating and applied on Al substrate. Inhibition efficiency was studied by electrochemical impedance spectroscopy (EIS). The results demonstrate that for the lithium carbonate, alumina shell can be formed in the surface via ALD process and a reduced leaching can be observed in the case of coated Li2CO3; healing effect can be observed in the encapsulated Li2CO3 doped coating, indicating the feasibility of this encapsulation concept on lithium carbonate. For the cerium nitrate, the inhibitor was coated with organic coating via MLD process but not well coated via ALD process; reduced leaching was not observed in this case and healing effect was not observed, neither. Organic shell can be well formed in the surface of 2-MBT, but the coating was not stable enough in solution to reduce leaching of the inhibitor; inhibition efficiency was not increased by doping the encapsulated 2-MBT into epoxy coating, possibly due to the reaction between shell material and epoxy coating.Mechanical, Maritime and Materials EngineeringMaterials Science and Engineerin
Tailoring the flow properties of inhaled micronized drug powders by atomic and molecular layer deposition
No full textFor dry powder inhaled formulations, good flow behaviour is vital in re-dispersing the powder. However, inhaled drug powders with a particle size below 10 µm are classified as highly cohesive materials with poor flow characteristics. Here we demonstrate how to alter the flow properties of micronized budesonide powders by depositing different materials (organic, inorganic, and hybrid organic–inorganic) in the forms of nanoscale films onto the drug particles using atomic/molecular layer deposition (ALD/MLD) coatings. The angle of repose (static) and pneumatic delivery measurements were performed to access the flow characteristics. The flowability can be effectively improved with the growth of inorganic nanofilm (SiO2, TiO2, or Al2O3) via ALD and hybrid nanofilm (titanicone) via combined ALD-MLD coating. This improvement is reflected by the decrease in the angle of repose and minimum pick-up velocity (Upu), as well as promoting the pneumatic delivery of a much larger amount of drug powders after ALD or hybrid coating. In contrast, the organic PET coated budesonide via MLD exhibits comparable poor flow characteristics as the uncoated budesonide. Rather than being transported in individual particles, the uncoated or PET-coated budesonide powders are pneumatically delivered in form of complex clusters with a size of over 500 μm, whereas the ALD budesonide is dispersed in form of small agglomerates (<100 μm). Despite the difference in agglomerate size, entraining behaviors of all samples agree well with the prediction of Kalman's pick-up Zone I correlation. The inorganic nanofilm deposited via ALD alters the surface chemistry to reduce the inter-particle forces measured by atomic force microscopy, giving rise to an improved drug delivery performance. Nanoscale surface modification of dry powder particles has good potential for inhaled drug delivery enhancement.ChemE/Product and Process Engineerin
Sub-nanoscale Surface Engineering of TiO<sub>2</sub>Nanoparticles by Molecular Layer Deposition of Poly(ethylene terephthalate) for Suppressing Photoactivity and Enhancing Dispersibility
No full textIn this work, we report molecular layer deposition (MLD) of ultrathin poly(ethylene terephthalate) (PET) films on gram-scale batches of ultrafine particles for the first time. TiO2 P25 nanoparticles (NPs) are coated up to 50 cycles in an atmospheric-pressure fluidized-bed reactor at 150 °C using terephthaloyl chloride and ethylene glycol as precursors. Ex-situ diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis, and transmission electron microscopy show the linear growth at 0.05 nm/cycle of uniform and conformal PET films, which are unattainable with conventional wet-phase approaches. The sub-nanoscale and nanoscale PET films not only suppress the photocatalytic activity of TiO2 NPs by hindering the access of water and reactant molecules to the TiO2 surface but also improve the dispersibility of TiO2 NPs in both organic and aqueous media. Still, the bulk optical properties, electronic structure, and surface area of TiO2 are essentially unaffected by the MLD process. This study demonstrates the industrial relevance of MLD to simultaneously suppress the photoactivity and enhance the dispersibility of commercial TiO2 P25 nanopowders, which is crucial for their use for example as UV-screening agents in sunscreens and as white pigments in paints. Moreover, by rapidly modifying the surface properties of particles in a controlled manner at the sub-nanometer scale, particle MLD can serve many other applications ranging from nanofluids to emulsions to polymer nanocomposites.ChemE/Product and Process EngineeringBT/Biocatalysi
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