HiDAnet: RGB-D Salient Object Detection via Hierarchical Depth Awareness.

RGB-D saliency detection aims to fuse multi-modal cues to accurately localize salient regions. Existing works often adopt attention modules for feature modeling, with few methods explicitly leveraging fine-grained details to merge with semantic cues. Thus, despite the auxiliary depth information, it is still challenging for existing models to distinguish objects with similar appearances but at distinct camera distances. In this paper, from a new perspective, we propose a novel Hierarchical Depth Awareness network (HiDAnet) for RGB-D saliency detection. Our motivation comes from the observation that the multi-granularity properties of geometric priors correlate well with the neural network hierarchies. To realize multi-modal and multi-level fusion, we first use a granularity-based attention scheme to strengthen the discriminatory power of RGB and depth features separately. Then we introduce a unified cross dual-attention module for multi-modal and multi-level fusion in a coarse-to-fine manner. The encoded multi-modal features are gradually aggregated into a shared decoder. Further, we exploit a multi-scale loss to take full advantage of the hierarchical information. Extensive experiments on challenging benchmark datasets demonstrate that our HiDAnet performs favorably over the state-of-the-art methods by large margins. The source code can be found in https://github.com/Zongwei97/HIDANet/.

Self-assembled nanostructured cellulose prepared by a dissolution and regeneration process using phosphoric acid as a solvent.

This report describes a "green" method for preparing self-assembled nanostructured cellulose through a dissolution and regeneration process. Cold phosphoric acid is used to dissolve cellulose in order to convert crystalline cellulose into its molecular form. Self-assembly of cellulose molecules into nanostructured cellulose is achieved by using water to regenerate cellulose. By controlling the temperature and time of the phosphoric acid treatment between dissolution and regeneration, the degree of polymerization and the degree of substitution of phosphorous for the regenerated celluloses can be tuned. As a result, cellulose nanofibers or nanospheres can be obtained when the treatment temperature is set to 5 or 50°C, respectively. X-ray analysis shows that the cellulose nanofibers are amorphous and that the cellulose nanospheres are structured similarly to cellulose II with crystallinity indexes between 56 and 73%. Our method offers a "green" process for preparing nanostructured celluloses in high yields.

Stabilizing oil-in-water emulsions with regenerated chitin nanofibers.

Natural chitin is a highly crystalline biopolymer with poor aqueous solubility. Thus direct application of chitin is rather limited unless chemical modifications are made to improve its solubility in aqueous media. Through a simple dissolution and regeneration process, we have successfully prepared chitin nanofibers with diameters around 50nm, which form a stable suspension at concentrations higher than 0.50% and a self-supporting gel at concentrations higher than 1.00%. Additionally, these nanofibers can stabilize oil-in-water emulsions with oil fraction more than 0.50 at chitin usage level of 0.01g/g oil. The droplet sizes of the resulting emulsions decrease with increasing chitin concentrations and decreasing oil fraction. Confocal laser scanning micrographs demonstrate the adsorption of chitin nanofibers on the emulsion droplet surface, which indicates the emulsion stabilization is through a Pickering mechanism. Our findings allow the direct application of chitin in the food industry without chemical modifications.

Designed nucleus penetrating thymine-capped dendrimers: a potential vehicle for intramuscular gene transfection.

A nucleus penetrating vehicle is indispensible when seeking to deliver plasmid DNA for gene transfection. In this study, dendrimers with terminal thymine groups were synthesized to meet this objective. Through modifications of the hydrophilic and neutral thymine moieties on hyperbranched peripheries, these dendrimers can achieve biosafety, efficient endosomal escape ability, cytosolic accessibility, and eventually, nuclear entry for the purposes of gene transfection. After optimization of the thymine coverages, better gene expression can only be achieved while replacing ∼50% of the amine groups of a dendrimer with thymine moieties. Presumably, a specific dendrimer comprising thymine and primary amines might possess a synergistic effect to promote pDNA condensation via the cooperation of electrostatic interaction and hydrogen bonding. In comparison, a dendrimer entirely capped by thymine can lose external amines, decreasing pDNA complexity and stability, which would cause poor gene transfection. The utility of specific thymine-capped dendrimers in vivo level was demonstrated to successfully and efficiently deliver plasmid DNA at a low complex ratio into mouse muscle by intramuscular injection. Upon the easy accessibility of intramuscular administration, the capability of thymine-capped dendrimers might be potentially used in immunotherapeutic gene transfection in the future.

Co-caged gold nanoclusters and methyl motifs lead to detoxification of dendrimers and allow cytosolic access for siRNA transfection.

Nonviral vectors used in gene delivery, such as cationic polymers and dendrimers, exhibit problems of inherent toxicity and inefficient cytosolic access that must be overcome. In this work, a simple co-caging strategy focused on overcoming the two limitations of dendrimers for siRNA transfection is reported. By embedding gold nanoclusters within a dendrimer, the structure of the dendrimer becomes compact and allows an irreversible backfolding of exterior primary amines from the branch to the core, which dramatically eliminates dendrimer toxicity and enhances safety. Gold nanoclusters with strong emissions can confer a trackable function to dendrimers acting as a transfection vector (TV) for siRNA transfection. In order to maximize efficiency of complexing with siRNA, the TV further incorporated caged methyl motifs, transforming the partially tertiary amines into quaternary ammonium ions to form a methylated TV (MTV). The cellular responses to the MTV were similar to those of the TV, but the responses to the MTV can also enhance cytosolic access to better deliver siRNA for mRNA knockdown. This finding offers a novel perspective to facilitate the use of various cationic polymers for detoxification in biological applications through a co-caging strategy without further chemical modifications.

Recent progress in copolymer-mediated siRNA delivery.

RNAi-mediated gene silencing has great potential for treating various diseases, including cancer, by delivering a specific short interfering RNA (siRNA) to knock down pathogenic mRNAs and suppress protein translation. Although many researchers are dedicated to devising polymer-based vehicles for exogenous in vitro siRNA transfection, few synthetic vehicles are feasible in vivo. Recent studies have presented copolymer-based vectors that are minimally immunogenic and facilitate highly efficient internalizing of exogenous siRNA, compared with homopolymer-based vectors. Cationic segments, organelle-escape units, and degradable fragments are essential to a copolymer-based vehicle for siRNA delivery. The majority of these cationic segments are derived from polyamines, including polylysine, polyarginine, chitosan, polyethylenimines and polyamidoamine dendrimers. Not only do these cationic polyamines protect siRNA, they can also promote disruption of endosomal membranes. Degradable fragments of copolymers must be derived from various polyelectrolytes to release the siRNA once the complexes enter the cytoplasm. This review describes recent progress in copolymer-mediated siRNA delivery, including various building blocks for biocompatible copolymers for efficient in vitro siRNA delivery, and a useful basis for addressing the challenges of in vivo siRNA delivery.

5,5'-Bis[(2,2,2-trifluoro-eth-oxy)meth-yl]-2,2'-bipyridine.

The complete molecule of the title compound, C(16)H(14)F(6)N(2)O(2), is generated by crystallographic inversion symmetry, which results in two short intramolecular C-H⋯N hydrogen-bond contacts per molecule. In the crystal, aromatic π-π stacking [centroid-centroid distance = 3.457 (2) Å] and weak C-H⋯π inter-actions occur. A short H⋯H [2.32 (3) Å] contact is present.

4,4'-Bis(2,2,2-trifluoroethoxymethyl)-2,2'-bipyridine.

As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C(16)H(14)F(6)N(2)O(2), contains the smallest fluorinated group, viz. CF(3). The molecule resides on a crystallographic inversion centre at the mid-point of the pyridine C(ipso)-C(ipso) bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C-H...N and C-H...O interactions are observed, similar to those in related polyfluorinated bpy-metal complexes. A pi-pi interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C-H...N hydrogen bonding is present between one of the CF(3)CH(2)- methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl-type C-H...F interactions to atoms of the terminal CF(3) group. It is of note that the O-CH(2)CF(3) bond is almost perpendicular to the bpy plane.