Interfacial nucleation in iPP/PB-1 blends promotes the formation of polybutene-1 trigonal crystals

The formation of trigonal Form I\ub4 crystals of polybutene-1 (PB-1) directly from melt has drawn much attention in past decades. In this study, we investigate the fractionated crystallization behavior of PB-1 within droplets formed by blending PB-1 with an excess of isotactic polypropylene (iPP) employing DSC, SEM, in situ synchrotron WAXD and FT-IR. When PB-1 is dispersed into a large number of small size droplets, the heterogeneous nucleation of Form II crystals can be inhibited because the number of droplets is larger than that of active nucleation sites for Form II (i.e., active heterogeneities originally present in bulk PB-1). The nucleation of the finely dispersed PB-1 droplets does not occur homogenously, but at the interface with the iPP matrix, which induces the crystallization of the droplets into Form I\ub4. The crystallization rate of Form I\ub4 at different temperatures was determined by Fourier transform infrared spectroscopy. It was found that trigonal Form I\ub4 crystallizes faster when the content of PB-1 in the blend is lower, and the specific interfacial surface area is larger. The opposite effect has been observed for the kinetics of the metastable Form II formation. It is therefore suggested that Form I\ub4 crystallization is driven by the nucleation of PB-1 at the crystalline iPP surface, which competes with the crystallization of Form II induced by nucleating heterogeneities present in PB-1 droplets

Characterization of Near Full-Length Transmitted/Founder HIV-1 Subtype D and A/D Recombinant Genomes in a Heterosexual Ugandan Population (2006-2011).

Detailed characterization of transmitted HIV-1 variants in Uganda is fundamentally important to inform vaccine design, yet studies on the transmitted full-length strains of subtype D viruses are limited. Here, we amplified single genomes and characterized viruses, some of which were previously classified as subtype D by sub-genomic pol sequencing that were transmitted in Uganda between December 2006 to June 2011. Analysis of 5' and 3' half genome sequences showed 73% (19/26) of infections involved single virus transmissions, whereas 27% (7/26) of infections involved multiple variant transmissions based on predictions of a model of random virus evolution. Subtype analysis of inferred transmitted/founder viruses showed a high transmission rate of inter-subtype recombinants (69%, 20/29) involving mainly A1/D, while pure subtype D variants accounted for one-third of infections (31%, 9/29). Recombination patterns included a predominance of subtype D in the gag/pol region and a highly recombinogenic envelope gene. The signal peptide-C1 region and gp41 transmembrane domain (Tat2/Rev2 flanking region) were hotspots for A1/D recombination events. Analysis of a panel of 14 transmitted/founder molecular clones showed no difference in replication capacity between subtype D viruses (n = 3) and inter-subtype mosaic recombinants (n = 11). However, individuals infected with high replication capacity viruses had a faster CD4 T cell loss. The high transmission rate of unique inter-subtype recombinants is striking and emphasizes the extraordinary challenge for vaccine design and, in particular, for the highly variable and recombinogenic envelope gene, which is targeted by rational designs aimed to elicit broadly neutralizing antibodies

ETR2 is an ETR1-like gene involved in ethylene signaling in Arabidopsis

The plant hormone ethylene regulates a variety of processes of growth and development. To identify components in the ethylene signal transduction pathway, we screened for ethylene-insensitive mutants in Arabidopsis thaliana and isolated a dominant etr2-1 mutant. The etr2-1 mutation confers ethylene insensitivity in several processes, including etiolated seedling elongation, leaf expansion, and leaf senescence. Double mutant analysis indicates that ETR2 acts upstream of CTR1, which codes for a Raf-related protein kinase. We cloned the ETR2 gene on the basis of its map position, and we found that it exhibits sequence homology to the ethylene receptor gene ETR1 and the ETR1-like ERS gene. ETR2 may thus encode a third ethylene receptor in Arabidopsis, transducing the hormonal signal through its “two-component” structure. Expression studies show that ETR2 is ubiquitously expressed and has a higher expression in some tissues, including inflorescence and floral meristems, petals, and ovules

Hybrid diffusion imaging reveals altered white matter tract integrity and associations with symptoms and cognitive dysfunction in chronic traumatic brain injury.

The detection and association of in vivo biomarkers in white matter (WM) pathology after acute and chronic mild traumatic brain injury (mTBI) are needed to improve care and develop therapies. In this study, we used the diffusion MRI method of hybrid diffusion imaging (HYDI)to detect white matter alterations in patients with chronic TBI (cTBI). 40 patients with cTBI presenting symptoms at least three months post injury, and 17 healthy controls underwent magnetic resonance HYDI. cTBI patients were assessed with a battery of neuropsychological tests. A voxel-wise statistical analysis within the white matter skeleton was performed to study between group differences in the diffusion models. In addition, a partial correlation analysis controlling for age, sex, and time after injury was performed within the cTBI cohort, to test for associations between diffusion metrics and clinical outcomes. The advanced diffusion modeling technique of neurite orientation dispersion and density imaging (NODDI) showed large clusters of between-group differences resulting in lower values in the cTBI across the brain, where the single compartment diffusion tensor model failed to show any significant results. However, the diffusion tensor model appeared to be just as sensitive in detecting self-reported symptoms in the cTBI population using a within-group correlation. To the best of our knowledge this study provides the first application of HYDI in evaluation of cTBI using combined DTI and NODDI, significantly enhancing our understanding of the effects of concussion on white matter microstructure and emphasizing the utility of full characterization of complex diffusion to diagnose, monitor, and treat brain injury