A pH‐Switchable Triple Hydrogen‐Bonding Motif

A stimuli responsive linear hydrogen bonding motif, capable of in situ protonation and deprotonation, has been investigated. The interactions of the responsive hydrogen bonding motif with complementary partners were examined through a series of 1H NMR experiments, revealing that the recognition preference of the responsive hydrogen bonding motif in a mixture can be switched between two states

Numerical modeling of the impact of pump wavelength on Yb-doped fiber amplifier performance

Ytterbium-doped optical amplifiers have become common tools for industrial applications due to their high efficiency, relatively low cost and potentially very high output power level. The efficiency of an ytterbium-doped fiber amplifier depends mainly on the absorption of pump radiation, and, therefore, optimum pump wavelengths have been proposed such as 915 nm. However, the semiconductor pump diodes batch supplied by manufacturers may exhibit a spread in the output wavelength. This paper theoretically investigates the performance of Yb-doped amplifiers for different pump wavelengths and defines the pump power penalty when the pump source does not emit at the optimum wavelength. The penalty has been defined as normalized excess pump power required to achieve the desired gain

Role of defects and disorder in the half-metallic full-Heusler compounds

Half-metallic ferromagnets and especially the full-Heusler alloys containing Co are at the center of scientific research due to their potential applications in spintronics. For realistic devices it is important to control accurately the creation of defects in these alloys. We review some of our late results on the role of defects and impurities in these compounds. More precisely we present results for the following cases (i) doping and disorder in Co$_2$Cr(Mn)Al(Si) alloys, (ii) half-metallic ferrimagnetism appeared due to the creation of Cr(Mn) antisites in these alloys, (iii) Co-doping in Mn$_2$VAl(Si) alloys leading to half-metallic antiferromagnetism, and finally (iv) the occurrence of vacancies in the full-Heusler alloys containing Co and Mn. These results are susceptible of encouraging further theoretical and experimental research in the properties of these compounds.Comment: Chapter intended for a book with contributions of the invited speakers of the International Conference on Nanoscale Magnetism 2007. Revised version contains new figure

Supramolecular Self‐Sorting Networks using Hydrogen‐Bonding Motifs

A current objective in supramolecular chemistry is to mimic the transitions between complex self‐sorted systems that represent a hallmark of regulatory function in nature. In this work, a self‐sorting network, comprising linear hydrogen motifs, was created. Selecting six hydrogen‐bonding motifs capable of both high‐fidelity and promiscuous molecular recognition gave rise to a complex self‐sorting system, which included motifs capable of both narcissistic and social self‐sorting. Examination of the interactions between individual components, experimentally and computationally, provided a rationale for the product distribution during each phase of a cascade. This reasoning holds through up to five sequential additions of six building blocks, resulting in the construction of a biomimetic network in which the presence or absence of different components provides multiple unique pathways to distinct self‐sorted configurations

Adaptive hypermedia driven serious game design and cognitive style in school settings: an exploratory study

The potential value of adaptive hypermedia and game based learning to education and training has long been recognised, numerous studies have been undertaken in both those areas investigating its potential to improve learner performance. In particular research has indicated that tailoring content to match the prior knowledge of the user has the power to increase the effectiveness of learning systems. Recent studies have begun to indicate that Adaptive Hypermedia Learning Systems (AHLS) based on cognitive styles have the power to improve learner performance. Recent examples of research exploring avenues for effectively incorporating serious games into AHLS indicated that integrating serious games into a personalized learning environment has the potential educational benefits of combining a personalized delivery with increased learner motivation. The exploratory study presented in this paper here developed an Adaptive Hypermedia Driven Serious Game (AHDSG) based around Pask’s Holist-Serialist dimension of cognitive style. A prototype AHDSG was designed and developed to teach students about Sutton Hoo and archaeological methods. Sixty-six secondary school students participated in this study. Overall the findings of this study show that there was an improvement in performance among all participants. Although the participants that used the system which adapted to their preferred cognitive style achieved a higher mean gain score, the difference was not significant

Advancing stem cell technologies for conservation of wildlife biodiversity.

Wildlife biodiversity is essential for healthy, resilient and sustainable ecosystems. For biologists, this diversity also represents a treasure trove of genetic, molecular and developmental mechanisms that deepen our understanding of the origins and rules of life. However, the rapid decline in biodiversity reported recently foreshadows a potentially catastrophic collapse of many important ecosystems and the associated irreversible loss of many forms of life on our planet. Immediate action by conservationists of all stripes is required to avert this disaster. In this Spotlight, we draw together insights and proposals discussed at a recent workshop hosted by Revive & Restore, which gathered experts to discuss how stem cell technologies can support traditional conservation techniques and help protect animal biodiversity. We discuss reprogramming, in vitro gametogenesis, disease modelling and embryo modelling, and we highlight the prospects for leveraging stem cell technologies beyond mammalian species

HIV-1 Efficient Entry in Inner Foreskin Is Mediated by Elevated CCL5/RANTES that Recruits T Cells and Fuels Conjugate Formation with Langerhans Cells

Male circumcision reduces acquisition of HIV-1 by 60%. Hence, the foreskin is an HIV-1 entry portal during sexual transmission. We recently reported that efficient HIV-1 transmission occurs following 1 h of polarized exposure of the inner, but not outer, foreskin to HIV-1-infected cells, but not to cell-free virus. At this early time point, Langerhans cells (LCs) and T-cells within the inner foreskin epidermis are the first cells targeted by the virus. To gain in-depth insight into the molecular mechanisms governing inner foreskin HIV-1 entry, foreskin explants were inoculated with HIV-1-infeceted cells for 4 h. The chemokine/cytokine milieu secreted by the foreskin tissue, and resulting modifications in density and spatial distribution of T-cells and LCs, were then investigated. Our studies show that in the inner foreskin, inoculation with HIV-1-infected cells induces increased CCL5/RANTES (1.63-fold) and decreased CCL20/MIP-3-alpha (0.62-fold) secretion. Elevated CCL5/RANTES mediates recruitment of T-cells from the dermis into the epidermis, which is blocked by a neutralizing CCL5/RANTES Ab. In parallel, HIV-1-infected cells mediate a bi-phasic modification in the spatial distribution of epidermal LCs: attraction to the apical surface at 1 h, followed by migration back towards the basement membrane later on at 4 h, in correlation with reduced CCL20/MIP-3-alpha at this time point. T-cell recruitment fuels the continuous formation of LC-T-cell conjugates, permitting the transfer of HIV-1 captured by LCs. Together, these results reveal that HIV-1 induces a dynamic process of immune cells relocation in the inner foreskin that is associated with specific chemokines secretion, which favors efficient HIV-1 entry at this site

Cover Feature: Supramolecular Self‐Sorting Networks using Hydrogen‐Bonding Motifs (Chem. Eur. J. 3/2019)

A self‐sorting network comprising six different hydrogen bonding‐motifs is presented. Detailed analysis of the pairwise molecular recognition behavior of each hydrogen‐bonding motif by NMR spectroscopy, single‐crystal studies, and DFT allowed the construction of cascades exploiting integrative and non‐integrative narcissistic and social self‐sorted product distributions. Multiple distinct pathways within the network could be created depending on the presence or absence of different components. More information can be found in the Full Paper by C. Fonseca Guerra, A. J. Wilson, et al. on page 785-795