A pseudo-Double-Network Hydrogel Built upon Layered Double Hydroxides with Self-Strengthening Properties

While great achievements have been made in the development of mechanically robust nanocomposite hydrogels, incorporating multiple interactions on the bases of two demensional inorganic cross-linkers to construct self-strengthening hydrogels has rarely been investigated. To this end, we propose here a new method for the coupling the dynamic covalent bonds and non-covalent interactions within a pseudo double-network system. The pseudo first network, formed through the Schiff Base reation between Tris-modified layered double hydroxides (Tris-LDHs) and oxidized dextran (ODex), is linked to the second network built upon non-covalent interactions between Tris-LDHs and poly(acrylamide-co-2-acrylamido-2-methyl-propanesulfonate) (p-(AM-co-AMPS). The swelling and mechanical properties of the resulting hydrogels have been investigated as a function of the ODex and AMPS contents. The as-prepared hydrogel can swell to 420 times of its original size and retain more than 99.9 wt.% of water. Mechanical tests show that the hydrogel can bear 90 % of compression and is able to be stretched to near 30 times of its original length. Cyclic tensile tests reveal that the hydrogels are capable of self-strengthening after mechanical training. The unique energy dissipation mechanism based on the dynamic covalent and non-covalent interactions is considered to be responsible for the outstanding swelling and mechanical performances.

Direct molecular confinement in layered double hydroxides: from fundamental to advanced photo-luminescent hybrid materials

We report here new approaches for the direct intercalation of layered double hydroxides (LDHs) from carbonate-LDHs by using various organic acids as proton sources for de-carbonation.

[Construction and characterization of normalized cDNA library of maize inbred Mo17 from multiple tissues and developmental stages]

Comprehensive complementary DNA (cDNA) library is a valuable resource for functional genomics. In this study, we set up a normalized cDNA library of Mo17 (MONL) by saturation hybridization with genomic DNA, which contained expressed genes of eight tissues and organs from inbred Mo17 of maize (Zea mays L.). In this library, the insert sizes range from 0.4 kb to 4 kb and the average size is 1.18 kb. 10.830 clones were spotted on nylon membrane to make a cDNA microarray. Randomly picked 300 clones from the cDNA library were sequenced. The cDNA microarry was hybridized with pooled tissue mRNA probes or housekeeping gene cDNA probes. The results showed the normalized cDNA library comprehensively includes tissue-specific genes in which 71% are unique ESTs (expressed sequence tags) based on the 300 sequences analyzed. Using BLAST program to compare the sequences against online nucleotide databases, 88% sequences were found in ZmDB or NCBI, and 12% sequences were not found in existing nucleotide databases. More than 73% sequences are of unknown function. The library could be extensively used in developing DNA markers, sequencing ESTs, mining new genes, identifying positional cloning and candidate gene, and developing microarrays in maize genomics research.

[Analysis of sequence and polymorphism of R in S-type CMS maize]

The S-type CMS of maize was reported to be caused by a DNA region designated R in mitochondrial genomes. Through PCR using artificial primers, 1 kb DNA fragments were obtained from mitochondrial DNA of Tangxu and WB cytoplasm. The DNA sequences are almost the same as the sequence in R region of CMS-S. Using the DNA fragment from Tangxu cytoplasm as probe to scan the Mo17 CMS-J gene library, several positive clones appeared. The clone B39 contains a 6.7 kb BamHI fragment with R region. Nucleotide sequence analysis found two orfs including the chimeric orf77. Seventeen lines of maize under Mo17 and 77 nuclear background including N, T, C, S four types of cytoplasm were used for RFLP. Three types of R were discovered in S-type CMS, but not in C group. The R in N group was different from that in S group. T group had only part of R region. The Southern blot of Tangxü and Shuang cytoplasm in R regions showed different ratio of R in different nuclear backgrounds. The heterogeneity of R region suggests that the organization and rearrangement of R controlled by the nuclear background. R region seems to be involved in the mechanism of S group CMS. Varieties of structures of R, the ratio of three R types, different DNA sequences in R region of different CMS might be concerned with instability of S-type CMS.

[Transcervical salpingography and tubal recanalization]

The results of transcervical salpingography and tubal recanalization by means of modified Thurmond and Rösch's technique were reported. Proximal tubal obstruction was diagnosed in 20 infertile women by X-ray hysterosalpingography and/or laparoscopy. Our results showed that tubal recanalization was achieved in 19(95%) of 20 patients, four patients became pregnanCy following the procedure. Distal tubal diseases were seen in 8 of 20 patients. Follow up studies revealed tubal patency was maintained in 7(54%) of 13 patients. The mean radiation dosage received by the patient was 6.35mGy. Compared with Thurmond and Rösch technique the modified technique has the advantage of decreasing the time of fluoroscopy and is a safe, effective and simple method for the diagnosis and treatment of infertile women with proximal tubal obstruction.