Abstract Goethite widely exists among ocean sediments; it plays an important role in fixing heavy metals and adsorbing organic contaminants. So the understanding of the adsorbing process of water molecule on its surfa...Abstract Goethite widely exists among ocean sediments; it plays an important role in fixing heavy metals and adsorbing organic contaminants. So the understanding of the adsorbing process of water molecule on its surface will be very helpful to further reveal such environmental friendly processes. The configuration, electronic properties and interaction energy of water molecules adsorbed on pnma goethite （010） surface were investigated in detail by using density functional theory on 6-31G （d,p） basis set and projec- tor-augment wave （PAW） method. The mechanism of the interaction between goethite surface and H20 was proposed. Despite the differences in total energy, there are four possible types of water molecule adsorption configurations on goethite （010） surface （Aa, Ab, Ba, Bb）, forming coordination bond with surface Fe atom. Results of theoretical modeling indicate that the dissociation process of adsorbed water is an endothermic reaction with high activation energy. The dissociation of adsorbed water molecule is a proton transportation process between water＇s O atoms and surface. PDOS results indicate that the bonding between 1-120 and （010） surface is due to the overlapping of water＇s 2p orbitals and Fe＇s 3d orbitals. These results clarify the mechanism on how adsorbed water is dissociated on the surface of goethite and potentially provide useful information of the surface chemistry of goethite.展开更多
This research was carried out in Iranian EFL （English as a foreign language） reading comprehension classes in an attempt to answer three research questions： （1） Does collaborative reading lead to greater comprehe...This research was carried out in Iranian EFL （English as a foreign language） reading comprehension classes in an attempt to answer three research questions： （1） Does collaborative reading lead to greater comprehension of a text than private reading？; （2） If so, what strategies are used by the students during collaborative reading？; and （3） In what ways might these strategies contribute to the higher level of comprehension？. A quasi-experimental design was used to answer the first question. The participants were pre-tested and streamed into two classes of equal reading comprehension abilities. The intervention consisted of four texts of equal length, comprising two rated in a pilot study as conceptually difficult/linguistically easy, and two rated as conceptually easy/linguistically difficult. The subjects in each class were involved in reading the two types of texts collaboratively and privately for four sessions. After reading the text, the subjects were asked to answer in writing 10 comprehension questions. Collaborative reading resulted in consistently and significantly higher scores than private reading for all four texts. Qualitative methods were employed to answer the last two questions. Group interactions during collaborative reading were tape recorded and transcribed, and 10 students selected at random from the two classes were interviewed in depth. Analysis of the group interaction transcripts revealed that the participants were using five major strategies in co-constructing meaning from the texts. These strategies included brainstorming, clarifying the language, summarizing, paraphrasing, and interaction management. Other minor （i.e., infrequent） strategies were also identified, such as making PCU/NCU （positive/negative claim to understand）, eliciting confirmation, and confirming.展开更多
基金financial supports from the National Natural Science Foundation of China (Nos.50673085,20677053)
文摘Abstract Goethite widely exists among ocean sediments; it plays an important role in fixing heavy metals and adsorbing organic contaminants. So the understanding of the adsorbing process of water molecule on its surface will be very helpful to further reveal such environmental friendly processes. The configuration, electronic properties and interaction energy of water molecules adsorbed on pnma goethite （010） surface were investigated in detail by using density functional theory on 6-31G （d,p） basis set and projec- tor-augment wave （PAW） method. The mechanism of the interaction between goethite surface and H20 was proposed. Despite the differences in total energy, there are four possible types of water molecule adsorption configurations on goethite （010） surface （Aa, Ab, Ba, Bb）, forming coordination bond with surface Fe atom. Results of theoretical modeling indicate that the dissociation process of adsorbed water is an endothermic reaction with high activation energy. The dissociation of adsorbed water molecule is a proton transportation process between water＇s O atoms and surface. PDOS results indicate that the bonding between 1-120 and （010） surface is due to the overlapping of water＇s 2p orbitals and Fe＇s 3d orbitals. These results clarify the mechanism on how adsorbed water is dissociated on the surface of goethite and potentially provide useful information of the surface chemistry of goethite.
文摘This research was carried out in Iranian EFL （English as a foreign language） reading comprehension classes in an attempt to answer three research questions： （1） Does collaborative reading lead to greater comprehension of a text than private reading？; （2） If so, what strategies are used by the students during collaborative reading？; and （3） In what ways might these strategies contribute to the higher level of comprehension？. A quasi-experimental design was used to answer the first question. The participants were pre-tested and streamed into two classes of equal reading comprehension abilities. The intervention consisted of four texts of equal length, comprising two rated in a pilot study as conceptually difficult/linguistically easy, and two rated as conceptually easy/linguistically difficult. The subjects in each class were involved in reading the two types of texts collaboratively and privately for four sessions. After reading the text, the subjects were asked to answer in writing 10 comprehension questions. Collaborative reading resulted in consistently and significantly higher scores than private reading for all four texts. Qualitative methods were employed to answer the last two questions. Group interactions during collaborative reading were tape recorded and transcribed, and 10 students selected at random from the two classes were interviewed in depth. Analysis of the group interaction transcripts revealed that the participants were using five major strategies in co-constructing meaning from the texts. These strategies included brainstorming, clarifying the language, summarizing, paraphrasing, and interaction management. Other minor （i.e., infrequent） strategies were also identified, such as making PCU/NCU （positive/negative claim to understand）, eliciting confirmation, and confirming.
