Ultrahigh molecular weight polyethylene is an engineering polymer that is widely used in demanding applications because of its unparallel properties such as high abrasion resistance, high-modulus and high-strength tapes and fibers, biaxial films, etc. In common practice, to achieve the uniaxial and the biaxial products, solution processing route is adopted to reduce the number of entanglement per chain. Another elegant route to reduce the number of entanglement is controlled polymerization using single-site catalytic system. In this publication, we address different polymerization conditions, temperature and time, to control molecular weight and the resultant entangled state. With the help of rheological studies, we show that heterogeneity in the distribution of entanglement along the chain during polymerization occurs. Because of living nature of the catalytic system, with increasing polymerization time molecular weight increases whereas the number of entanglement per unit chain decreases. These findings suggest that most of the entanglement is established at the initial stages of polymerization.

De novo mutations in ADNP, which encodes activity-dependent neuroprotective protein (ADNP), have recently been found to underlie Helsmoortel-Van der Aa syndrome, a complex neurological developmental disorder that also affects several other organ functions . ADNP is a putative transcription factor that is essential for embryonic development . However, its precise roles in transcriptional regulation and development are not understood. Here we show that ADNP interacts with the chromatin remodeller CHD4 and the chromatin architectural protein HP1 to form a stable complex, which we refer to as ChAHP. Besides mediating complex assembly, ADNP recognizes DNA motifs that specify binding of ChAHP to euchromatin. Genetic ablation of ChAHP components in mouse embryonic stem cells results in spontaneous differentiation concomitant with premature activation of lineage-specific genes and in a failure to differentiate towards the neuronal lineage. Molecularly, ChAHP-mediated repression is fundamentally different from canonical HP1-mediated silencing: HP1 proteins, in conjunction with histone H3 lysine 9 trimethylation (H3K9me3), are thought to assemble broad heterochromatin domains that are refractory to transcription. ChAHP-mediated repression, however, acts in a locally restricted manner by establishing inaccessible chromatin around its DNA-binding sites and does not depend on H3K9me3-modified nucleosomes. Together, our results reveal that ADNP, via the recruitment of HP1 and CHD4, regulates the expression of genes that are crucial for maintaining distinct cellular states and assures accurate cell fate decisions upon external cues. Such a general role of ChAHP in governing cell fate plasticity may explain why ADNP mutations affect several organs and body functions and contribute to cancer progression. Notably, we found that the integrity of the ChAHP complex is disrupted by nonsense mutations identified in patients with Helsmoortel-Van der Aa syndrome, and this could be rescued by aminoglycosides that suppress translation termination . Therefore, patients might benefit from therapeutic agents that are being developed to promote ribosomal read-through of premature stop codons.

No abstract

Unlike inorganic and organic molecules, in semicrystalline polymers melting gets complicated because of the requirement of conformational transformation of the chain segments, where part of the same chain resides in the crystal and also in the amorphous phase. The chain segment residing in the amorphous part can be constrained, either due to adjacent or nonadjacent re-entry leading to a different nature of chain folding, and arising differences are observed in local chain mobility due to differences in topological constraints. Thus, different conformational possibilities in the amorphous region of the semicrystalline polymer has implications on melting temperature and the processes involved in the order to the disorder phase transformation. With a series of experiments on ultra high molecular weight polyethylene, where the topological constraints are tailored by adopting a different synthesis route, it is shown that melting behavior cannot be fully explained by Gibbs–Thomson equation only. Nonlinearity in melting temperature on heating rate invokes kinetics in the melting process, where depending on the heating rate melting can occur either via successive detachment of chains and their diffusion in the melt or by cluster melting. The role of superheating on melting process is also addressed.

The codoping effect of Zn(2+) ions on luminescence emission in visible and near infrared (NIR) regions of Y2O3:Ho(3+)-Yb(3+) phosphor prepared by low temperature combustion process have been investigated under 980 nm and 448 nm excitations. The phase and crystallite size of the prepared phosphor were determined by X-ray diffraction analysis and processes involved in the upconversion mechanism have been discussed in detail via pump power dependence, decay curve analysis and a suitable energy level diagram. The temperature sensing performance of the developed material has also been investigated by measuring the fluorescence intensity ratio of the blue upconversion emission bands centred at 465 nm and 491 nm up to 673 K. It is found that by using fluorescence intensity ratio technique, appreciable sensitivity for temperature measurement can be achieved from the present phosphor material, which indicates its applicability as a high temperature sensing probe. The fabrication of green LEDs using the developed phosphor material has also been suggested.

These results demonstrate that RA patients have high levels of inflammatory markers, and these levels are correlated with the DAS28. These findings suggest a possible role of these markers in the pathogenesis of RA. Moreover, these biomarkers can be used as markers of disease activity in the diagnosis and treatment of RA.

No abstract

No abstract