Der längerfristige Einfluss von Tablets auf das Studium und die persönliche Lernumgebung Studierender

Der vorliegende Beitrag untersucht die Frage, wie sich die Bereitstellung eines Tablets über die Zeit von zwei Jahren auf die persönlichen Lernumgebung Studierender bzw. auf deren Studium auswirkt. In einer explorativen, standardisierten ‚Grundbefragung‘ schätzen gut 30 Studierende eines medienaffinen Studiengangs die Nutzung ihres Medienensembles ein, nachdem sie ein Tablet zwei bis zweieinhalb Jahre für Studium und Freizeit gleichermaßen genutzt haben. Die zentrale Frage ist dabei, welche Rolle ein Tablet für die Befragten und ihre Arbeitsabläufe im weiten Kontext Studium tatsächlich spielt. Neben der allgemeinen positiven Beurteilung durch die Studierenden zeigen sich in der konkreten Nutzung deutliche Einschränkungen auf deren Seite. Die Ergebnisse sind aufschlussreich hinsichtlich der aktuellen Medienverwendung Studierender sowie für die Gestaltung von Lehr- und Lernprozessen mit digitalen Medien und besonders mit mobilen Endgeräten. (DIPF/Orig.

The contribution of pUL74 to growth of human cytomegalovirus is masked in the presence of RL13 and UL128 expression

The glycoproteins gH and gL of human cytomegalovirus (HCMV) form a complex either with pUL74 (trimeric complex) or with proteins of the UL128 locus (pentameric complex). While the pentameric complex is dispensable for viral growth in fibroblasts, deletion of pUL74 causes a small plaque phenotype in HCMV lab strains, accompanied by greatly reduced cell-free infectivity. As HCMV isolates shortly after cultivation from clinical specimens do not release cell-free infectious virus, we wondered whether deletion of pUL74 would also affect virus growth in this background. To address this question, we took advantage of the BAC-cloned virus Merlin-RL13tetO that resembles such clinical isolates by growing cell-associated due to inducible expression of the viral RL13 gene. Stop codons were introduced by seamless mutagenesis into UL74 and/or the UL128 locus to abolish expression of the trimeric or pentameric complex, respectively. Virus mutants were reconstituted by transfection of the respective genomes into cultured cells and analyzed regarding focal growth. When the UL128 locus was intact, deletion of pUL74 did not notably affect focal growth of Merlin, irrespective of RL13 expression. In the absence of UL128 expression, foci were increased compared to wild type, and infectious cell-free virus was produced. Under these conditions, disruption of UL74 completely prevented virus spread from initially transfected cells to surrounding cells. In conclusion the contribution of pUL74 is masked when the UL128 locus is expressed at high levels, and its role in cell-free virus spread is only revealed when expression of the pentameric complex is inhibited

A Study in Red: The Overlooked Role of Azo‐Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

The unique optical and photoredox properties of heptazine-based polymeric carbon nitride (PCN) materials make them promising semiconductors for driving various productive photocatalytic conversions. However, their typical absorption onset at ca. 430–450 nm is still far from optimum for efficient sunlight harvesting. Despite many reports of successful attempts to extend the light absorption range of PCNs, the determination of the structural features responsible for the red shift of the light absorption edge beyond 450 nm has often been obstructed by the highly disordered structure of PCNs and/or low content of the moieties responsible for changes in optical and electronic properties. In this work, we implement a high-temperature (900 °C) treatment procedure for turning the conventional melamine-derived yellow PCN into a red carbon nitride. This approach preserves the typical PCN structure but incorporates a new functionality that promotes visible light absorption. A detailed characterization of the prepared material reveals that partial heptazine fragmentation accompanied by de-ammonification leads to the formation of azo-groups in the red PCN, a chromophore moiety whose role in shifting the optical absorption edge of PCNs has been overlooked so far. These azo moieties can be activated under visible-light (470 nm) for H₂ evolution even without any additional co-catalyst, but are also responsible for enhanced charge-trapping and radiative recombination, as shown by spectroscopic studies

Interferon-α Abrogates Tolerance Induction by Human Tolerogenic Dendritic Cells

BACKGROUND: Administration of interferon-α (IFN-α) represents an approved adjuvant therapy as reported for malignancies like melanoma and several viral infections. In malignant diseases, tolerance processes are critically involved in tumor progression. In this study, the effect of IFN-α on tolerance induction by human tolerogenic dendritic cells (DC) was analyzed. We focussed on tolerogenic IL-10-modulated DC (IL-10 DC) that are known to induce anergic regulatory T cells (iTregs). METHODOLOGY/PRINCIPAL FINDINGS: IFN-α promoted an enhanced maturation of IL-10 DC as demonstrated by upregulation of the differentiation marker CD83 as well as costimulatory molecules. IFN-α treatment resulted in an increased capacity of DC to stimulate T cell activation compared to control tolerogenic DC. We observed a strengthened T cell proliferation and increased IFN-γ production of CD4(+) and CD8(+) T cells stimulated by IFN-α-DC, demonstrating a restoration of the immunogenic capacity of tolerogenic DC in the presence of IFN-α. Notably, restimulation experiments revealed that IFN-α treatment of tolerogenic DC abolished the induction of T cell anergy and suppressor function of iTregs. In contrast, IFN-α neither affected the priming of iTregs nor converted iTregs into effector T cells. CONCLUSIONS/SIGNIFICANCE: IFN-α inhibits the induction of T cell tolerance by reversing the tolerogenic function of human DC

The only African wild tobacco, Nicotiana africana: Alkaloid content and the effect of herbivory

Herbivory in some Nicotiana species is known to induce alkaloid production. This study examined herbivore-induced defenses in the nornicotine-rich African tobacco N. africana, the only Nicotiana species indigenous to Africa. We tested the predictions that: 1) N. africana will have high constitutive levels of leaf, flower and nectar alkaloids; 2) leaf herbivory by the African bollworm Helicoverpa armigera will induce increased alkaloid levels in leaves, flowers and nectar; and 3) increased alkaloid concentrations in herbivore-damaged plants will negatively affect larval growth. We grew N. africana in large pots in a greenhouse and exposed flowering plants to densities of one, three and six fourth-instar larvae of H. armigera, for four days. Leaves, flowers and nectar were analyzed for nicotine, nornicotine and anabasine. The principal leaf alkaloid was nornicotine (mean: 28 µg/g dry mass) followed by anabasine (4.9 µg/g) and nicotine (0.6 µg/g). Nornicotine was found in low quantities in the flowers, but no nicotine or anabasine were recorded. The nectar contained none of the alkaloids measured. Larval growth was reduced when leaves of flowering plants were exposed to six larvae. As predicted by the optimal defense theory, herbivory had a localized effect and caused an increase in nornicotine concentrations in both undamaged top leaves of herbivore damaged plants and herbivore damaged leaves exposed to one and three larvae. The nicotine concentration increased in damaged compared to undamaged middle leaves. The nornicotine concentration was lower in damaged leaves of plants exposed to six compared to three larvae, suggesting that N. africana rather invests in new growth as opposed to protecting older leaves under severe attack. The results indicate that the nornicotine-rich N. africana will be unattractive to herbivores and more so when damaged, but that potential pollinators will be unaffected because the nectar remains alkaloid-free even after herbivory

Hydrology needed to manage droughts: the 2015 European case

Hydrology needed to manage droughts: the 2015 European cas

Climate change and possible challenges for crop protection – Yesterday, today, tomorrow

Das Klima und die Witterung sind prägende Faktoren für den Pflanzenschutz. Bereits vor 100 Jahren haben sich Wissenschaftler im Nachrichtenblatt für den Deutschen Pflanzenschutzdienst dieser Thematik gewidmet. Die Auswirkungen des Klimawandels sind ambivalent und es wird insgesamt zu einer Veränderung des Schaderregerspektrums kommen. Tendenziell werden Schäden durch Insekten, Krankheitserreger und wärmetolerante Unkräu­ter begünstigt. Das Risiko der Etablierung invasiver Arten nimmt zu. Ebenso kann die Wirksamkeit des biologischen Pflanzenschutzes beeinträchtigt und neue Verfahren erforderlich werden. Beim chemischen Pflanzenschutz wird sich das Wirkstoffspektrum verschieben und die Anforderungen an Applikationstechnik und -termin steigen. Starkregen kann das Risiko des Austrags von Pflanzenschutzmitteln in die Umwelt steigern. Auch in Mitteleuropa kann es verstärkt zu Befall mit Vorratsschädlingen bereits im Feld kommen und die Qualität und Lagerstabilität der Ernteprodukte abnehmen. Ins­gesamt wird die Bedeutung präventiver Pflanzenschutzmaßnahmen zunehmen. Die Folgen des Klimawandels erhöhen die betriebs- und volkswirtschaftlichen Risiken und stellen alle Akteursebenen vor erhebliche Heraus­forderungen.Climate and weather are decisive factors for plant protection. Already 100 years ago, scientists dedicated themselves to this topic in the newsletter of the German Plant Protection Service. The effects of climate change are ambi­valent and there will be an overall change in the pest spectrum. Damage caused by insects, pathogens and heat-tolerant weeds will tend to be favoured. The risk of invasive species becoming established increases. Simi­larly, the effectiveness of biological crop protection may be compromised and new methods may be required. In the case of chemical pesticides, the spectrum of active substances will shift and the demands on application technology and timing will increase. Heavy rains can increase the risk of pesticide run-off into the environment. There may be increased infestation with storage pests already in the field in Central Europe too, and the quality and storage stability of harvested products may decline. Overall, the importance of preventive plant protection measures will increase. The consequences of climate change increase operational and economic risks and pose considerable challenges for all levels of stakeholders