Effect of attentional selection on working memory for depth in a retro-cueing paradigm.

Recent studies have shown that the temporary storage and manipulation of depth information (working memory for depth; WMd) is largely different from that of visual information in a 2D context (visual working memory; VWM). Although there has been abundant evidence on VWM showing that cueing a memory item during retention could bias attention to its internal representation and thus improves its memory performance (a retro-cue effect), it is unknown whether such an effect differs for WMd that is nested in a 3D context compared with that in a conventional 2D context. Here, we used a change detection task to investigate the effect of attentional selection on WMd by testing several types of retro-cue. The memory array consisted of items positioned at various stereoscopic depth planes, and a cue was presented during retention. Participants needed to make judgments on whether the depth position of target (one memory item) had changed. Our study showed reliable valid retro-cue benefits but no invalid retro-cue cost, indicating that the relational information may be registered in WMd to prevent a strategical removal of the unattended item. There was also a slight improvement in memory performance for cueing depth order compared with that for cueing other feature dimensions or 2D locations. The attentional effect on memory representation in a 3D context is different from that in a 2D context, and the divergence may suggest the distinctive nature of working memory for depth.

Modulation of the driving forces for adsorption on MIL-101 analogues by decoration with sulfonic acid functional groups: superior selective adsorption of hazardous anionic dyes.

Toxic dyes pose a dramatic threat to human health and the environment when they are directly released into the water environment. Therefore, new porous materials with excellent adsorption performances are urgently needed to remove toxic dyes from wastewater. Herein, we report a sulfo-modified metal-organic framework (MIL-101-SO3H), which exhibits superior adsorption performance toward toxic dyes. The free -SO3H groups were successfully introduced into the MIL-101(Cr) skeleton to modulate the adsorption driving forces (i.e., hydrogen bonding, electrostatic attractions, and π-π stacking interactions together with adsorption spaces and steric hindrance) between the toxic dyes and MIL-101-SO3H adsorbent by varying the monosodium 2-sulfoterephthalic acid-to-terephthalic acid molar ratio in the reaction mixture. The experimental adsorption uptake by MIL-101-SO3H-1 was found to be 688.9 (methyl orange), 2592.7 (Congo red), and 213.2 (acid chrome blue K, AC) mg g-1, which was respectively 69.6, 89.6, and 51.5% higher than those of undecorated MIL-101. This adsorption behavior was attributed to the dye molecular structure, pore volumes, surface charge status, and functional groups of the adsorbents as well as the adsorption capacity of the dyes. The results revealed that the uncoordinated -SO3H groups increased the electrostatic attraction and hydrogen bonding between the MIL-101-SO3H adsorbent and linear anionic dyes. This increased the adsorption capacity toward the linear anionic dyes, overriding the effect of the pore volumes. On the other hand, the steric hindrance between the nonlinear anionic dye AC and MIL-101-SO3H adsorbent decreased the AC adsorption uptake of the latter, overriding the effects of hydrogen bonding and electrostatic attraction. In addition, the adsorption performance toward the cationic dye methylene blue increased, owing to the hydrogen bonding interactions, thereby overriding the effect of electrostatic repulsion and adsorption spaces. Thus, it is concluded that the adsorption behavior of the modified MIL-101-SO3H adsorbent is governed by the synergetic interplay between the electrostatic attraction, hydrogen bonding, and π-π stacking interactions as well as the steric hindrance and pore volumes of the adsorbent.