ABSTRACT
To evaluate the development of children's writing ability, it is necessary not only to examine quantitative indices such as the dependency distance, but also to inquiry the types of structures they use. We conducted clause boundary labeling using Support Vector Machine (SVM) on a corpus of Japanese students' compositions to investigate the change in the tendency of clause use with the progression of school age. The analysis of clause label frequency per sentence exhibited an increase in attributive clauses, nominal clauses, quotation clauses, and continuous clauses, and a decrease in parallel clauses, conditional clauses, reason clauses, time clauses, indirect interrogative clauses, and main clauses. The analysis of dependency distance demonstrated that most of the clauses that increased had short dependency distances, while most of the clauses that decreased had long dependency distances, and that the frequency of clauses with small dependency distances increased relatively with increasing school age. In addition, there was a shift in clause selection among functionally similar clauses, such as from "-te" to continuous forms, from "-tara" to "-ba", and from "-kedo" and "-keredo" to "-ga". These results suggest a change in the children's lexical and grammatical choices, from coordinate to subordinate structures, and from spoken to written vocabulary.
Subject(s)
Language , Writing , Child , Humans , Japan , Schools , StudentsABSTRACT
A novel polymer dispersant with a tri-block structure was designed. The tri-block polymer was composed of polyglycerin (PGL) with two dimethylpolysiloxane chains (DMPS) at both ends of the molecular structure. The high dispersibility of the dispersant was confirmed in both a model silica system and a sunscreen formulation. The apparent silica particle size was employed as an index for the dispensability for the dispersants. The novel dispersant showed 5 times more effective than conventional one. The flow properties of a sunscreen formulation containing titanium dioxide with the novel dispersant was Newtonian, indicating that the dispersibility of the dispersant was excellent. On the other hand, the formulation with conventional dispersant showed shear-thinning flow due to aggregation of the powder. These results mean that such a tri-block copolymer would make it possible to develop consumer demanded sunscreens.
Subject(s)
Phase Transition , Polymers/chemistry , Hydrophobic and Hydrophilic Interactions , Models, Chemical , Molecular Structure , Titanium/chemistry , ViscosityABSTRACT
Ultra-fine particles of titanium dioxide (TiO(2)) and zinc oxides (ZnO) are very attractive as UV-protecting ingredients in cosmetic products. The UV-scattering behavior of complex suspensions in a silicone oil is studied in relation to rheological properties. To control the dispersion stability of suspensions, three polyoxyethylene (POE)-modified silicones of branch-type, (AB)(n)-type, and ABA-type are used as dispersants. Irrespective of molecular structure, the dispersants can stabilize the TiO(2) and ZnO particles and the flow of both single suspensions is Newtonian with low viscosity. However, the Newtonian flow profiles and high dispersion states are maintained only for complex suspensions prepared with ABA-type dispersant. Since the POE groups which are incorporated between terminal silicones groups attach to the particle surfaces, the steric stabilization is responsible for low viscosity and high dispersions. Because the UV scattering of suspensions is determined by the sizes of flocculated structures, the high transmittance in the visible ranges and low transmittance in the UVA and UVB ranges can be achieved in the presence of ABA-type dispersant.
Subject(s)
Polyethylene Glycols/chemistry , Silicone Oils/chemistry , Sunscreening Agents/chemistry , Titanium/chemistry , Ultraviolet Rays , Zinc Oxide/chemistry , Rheology , SuspensionsABSTRACT
Ultrafine particles of titanium dioxide (TiO2) are very attractive as a UV protection ingredient in cosmetic products. The UV-scattering behavior of TiO2 suspensions in a silicone oil are studied in relation to rheological properties. To control the dispersion stability of suspensions, two types of polyether-modified silicones are used as dispersants. When the suspensions are prepared with branch-type dispersants in which the polyether groups are incorporated as side chains along the backbone, the flow is shear-thinning even at low shear rates. The appearance of plateaus in the frequency-dependence curves of storage modulus implies the solidlike responses. On the other hand, the suspensions prepared with linear conformation dispersants, in which the silicone group and polyether group are alternately repeated in one long chain, are Newtonian at low shear rates. The suspensions are regarded as liquids, because the storage modulus decreases rapidly in the low-frequency region. The suspension rheology is strongly associated with flocculated structures that are primarily controlled by the interparticle attractions. The differences in rheological behavior can be explained by the differences in the adsorbed conformation of dispersant silicones. From optical measurements, it is confirmed that UV scattering increases with decreasing flocculation degree. Therefore, good agreement is established between rheological properties and UV protection ability.
