Automated glycan assembly of arabinomannan oligosaccharides from Mycobacterium tuberculosis

Arabinomannan (AM) polysaccharides are clinical biomarkers for Mycobacterium tuberculosis (MTB) infections due to their roles in the interaction with host cells and interference with macrophage activation. Collections of defined AM oligosaccharides can help to improve the understanding of these polysaccharides and the development of novel therapeutical and diagnostic agents. Automated glycan assembly (AGA) was employed to prepare the core structure of AM from MTB, containing α-(1,6)-Man, α-(1,5)-Ara, and α-(1,2)-Man linkages. The introduction of a capping step after each glycosylation and further optimized reaction conditions allowed for the synthesis of a series of oligosaccharides, ranging from hexa- to branched dodecasaccharides

Understanding the bulk electronic structure of Ca1-xSrxVO3

We investigate the electronic structure of Ca1-xSrxVO3 using careful state-of-the-art experiments and calculations. Photoemission spectra using synchrotron radiation reveal a hitherto unnoticed polarization dependence of the photoemission matrix elements for the surface component leading to a substantial suppression of its intensity. Bulk spectra extracted with the help of experimentally determined electron escape depth and estimated suppression of surface contributions resolve outstanding puzzles concerning the electronic structure in Ca1-xSrxVO3.Comment: 4 pages including 3 figure

Passive Energy Recapture in Jellyfish Contributes to Propulsive Advantage over other Metazoans

Gelatinous zooplankton populations are well known for their ability to take over perturbed ecosystems. The ability of these animals to outcompete and functionally replace fish that exhibit an effective visual predatory mode is counterintuitive because jellyfish are described as inefficient swimmers that must rely on direct contact with prey to feed. We show that jellyfish exhibit a unique mechanism of passive energy recapture, which is exploited to allow them to travel 30% further each swimming cycle, thereby reducing metabolic energy demand by swimming muscles. By accounting for large interspecific differences in net metabolic rates, we demonstrate, contrary to prevailing views, that the jellyfish (Aurelia aurita) is one of the most energetically efficient propulsors on the planet, exhibiting a cost of transport (joules per kilogram per meter) lower than other metazoans. We estimate that reduced metabolic demand by passive energy recapture improves the cost of transport by 48%, allowing jellyfish to achieve the large sizes required for sufficient prey encounters. Pressure calculations, using both computational fluid dynamics and a newly developed method from empirical velocity field measurements, demonstrate that this extra thrust results from positive pressure created by a vortex ring underneath the bell during the refilling phase of swimming. These results demonstrate a physical basis for the ecological success of medusan swimmers despite their simple body plan. Results from this study also have implications for bioinspired design, where low-energy propulsion is required

Electronic Structure of Sr_2FeMoO_6

We have analysed the unusual electronic structure of Sr_2FeMoO_6 combining ab-initio and model Hamiltonian approaches. Our results indicate that there are strong enhancements of the intraatomic exchange strength at the Mo site as well as the antiferromagnetic coupling strength between Fe and Mo sites. We discuss the possibility of a negative effective Coulomb correlation strength (U_{eff}) at the Mo site due to these renormalised interaction strengths.Comment: To appear in Phys. Rev. Let

Usability Inspection Report of iLumina

iLumina is a digital library of sharable undergraduate teaching resource materials for science, mathematics, technology, and engineering being developed by the University of North Carolina at Wilmington (UNCW), Collegis, Virginia Tech, Georgia State University, Grand Valley State and The College of New Jersey. Types of iLumina resources include papers, tutorials, applets, presentations, visualizations, experiments, assignments, software, exercises

A Parade on Molecular Control of Flowering

Flower is a reproductive part of plant which contains complex array of functionally specialized structures.Photoperiodism, or the ability of an organism to detect day length, makes it possible for an event to occur at a particular time of year, thus allowing for a seasonal response. Circadian rhythms and photoperiodism have the common property of responding to cycles of light and darkness. Plant physiologists believed that the correlation between long days and flowering was a consequence of the accumulation of photosynthetic products synthesized during long days. Vernalization causes stable changes in the pattern of gene expression in the meristem, gene expression that are still stable even after vernalization is removed. The organ identity genes initially were identified through mutations that dramatically alter the structure and thus the identity of the floral organs produced in two adjacent whorls. The patterns of organ formation in the wild type and most of the mutant phenotypes are predicted and explained by ABC model of flower development. the transition to flowering involves a complex system of interacting factors that include among carbohydrates, gibberellins, cytokinins, bromeliads and ethylene

Low-Temperature Spin Dynamics of Doped Manganites: roles of Mn-t2g and eg and O-2p states

The low-temperature spin dynamics of doped manganites have been analyzed within a tight-binding model, the parameters of which are estimated by mapping the results of ab initio density functional calculations onto the model. This approach is found to provide a good description of the spin dynamics of the doped manganites, observed earlier within the ab initio calculations. Our analysis not only provides some insight into the roles of the eg and the t2g states but also indicates that the oxygen p states play an important role in the spin dynamics. This may cast doubt on the adaptability of the conventional model Hamiltonian approaches to the analysis of spin dynamics of doped manganites.Comment: 12 pages; Includes 5 figure

Electronic structure of NiS_{1-x}Se_x

We investigate the electronic structure of the metallic NiS$_{1-x}$Se$_x$ system using various electron spectroscopic techniques. The band structure results do not describe the details of the spectral features in the experimental spectrum, even for this paramagnetic metallic phase. However, a parameterized many-body multi-band model is found to be successful in describing the Ni~2$p$ core level and valence band, within the same model. The asymmetric line shape as well as the weak intensity feature in the Ni~2$p$ core level spectrum has been ascribed to extrinsic loss processes in the system. The presence of satellite features in the valence band spectrum shows the existence of the lower Hubbard band, deep inside the $pd$ metallic regime, consistent with the predictions of the dynamical mean field theory.Comment: To be published in Physical Review B, 18 pages and 5 figure