1,071 research outputs found

    Untersuchungen zur Verringerung von direkten Bekämpfungsmaßnahmen bei einigen Obstarten im biologischen Anbau

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    In the search for methods of reducing direct pest control in organic fruit growing, several farmers in South Tirol and Austria who have experience in this field were visited. At the same time, various cultivars of apple, pear and peach were observed in the research orchard of the Institute for Fruit Production and Horticulture at the University of Agricultural Sciences in Vienna. Clear differences among varieties with regard to their susceptibility to important pests and diseases were readily observable. The necessity of testing cultivars in organically managed systems using a minimum of direct plant protection was emphasized by many farmers. The farmer's experience and our own observations demonstrated that soil management, fertilization, rootstocks, forming and pruning also influence plant health and need to be taken more precisely into account in organic farming. Other important issues still to be considered include the study of suitable complementary plants for fruit trees and the connection between soil and tree health

    Semiheterogeneous Dual Nickel/Photocatalytic (Thio)etherification Using Carbon Nitrides

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    A carbon nitride material can be combined with homogeneous nickel catalysts for light-mediated cross-couplings of aryl bromides with alcohols under mild conditions. The metal-free heterogeneous semiconductor is fully recyclable and couples a broad range of electron-poor aryl bromides with primary and secondary alcohols as well as water. The application for intramolecular reactions and the synthesis of active pharmaceutical ingredients was demonstrated. The catalytic protocol is applicable for the coupling of aryl iodides with thiols as well

    Dichloromethylation of enones by carbon nitride photocatalysis

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    Small organic radicals are ubiquitous intermediates in photocatalysis and are used in organic synthesis to install functional groups and to tune electronic properties and pharmacokinetic parameters of the final molecule. Development of new methods to generate small organic radicals with added functionality can further extend the utility of photocatalysis for synthetic needs. Herein, we present a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K-PHI) photocatalyst under visible light irradiation for C1-extension of the enone backbone. The method is applied on 15 enones, with γ,γ-dichloroketones yields of 18–89%. Due to negative zeta-potential (−40 mV) and small particle size (100 nm) K-PHI suspension is used in quasi-homogeneous flow-photoreactor increasing the productivity by 19 times compared to the batch approach. The resulting γ,γ-dichloroketones, are used as bifunctional building blocks to access value-added organic compounds such as substituted furans and pyrroles

    A place for locative media: A theoretical framework for assessing locative media use in urban environments

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    By 2050, three quarters of the world’s population will live in large urban conurbations. Within these environments, we see the rise of locative media – mobile technologies that capture and deliver location- and time-specific content and connections to their users. The key attribute of locative media that distinguishes them from other mobile media is location. Yet ideas of how locative media influence our relationship to the spaces we inhabit remain undertheorized. This gap arises because of an absence of interrogation into how and why people come to develop a connection with these spaces – how and why a space becomes a place to which its inhabitants ascribe meaning and in which social relations occur among them. This thesis proposes a theoretical framework for interrogating locative media in the context of everyday, embodied and mobile urban place-making, to better analyze the opportunities and challenges afforded through locative media

    In situ Reaction Monitoring in Photocatalytic Organic Synthesis

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    Visible‐light photocatalysis provides numerous useful methodologies for synthetic organic chemistry. However, the mechanisms of these reactions are often not fully understood. Common mechanistic experiments mainly aim to characterize excited state properties of photocatalysts and their interaction with other species. Recently, in situ reaction monitoring using dedicated techniques was shown to be well‐suited for the identification of intermediates and to obtain kinetic insights, thereby providing more holistic pictures of the reactions of interest. This minireview surveys these technologies and discusses selected examples where reaction monitoring was used to elucidate the mechanism of photocatalytic reactions

    Emerging concepts in photocatalytic organic synthesis

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    Visible light photocatalysis has become a powerful tool in organic synthesis that uses photons as traceless, sustainable reagents. Most of the activities in the field focus on the development of new reactions via common photoredox cycles, but recently a number of exciting new concepts and strategies entered less charted territories. We survey approaches that enable the use of longer wavelengths and show that the wavelength and intensity of photons are import parameters that enable tuning of the reactivity of a photocatalysts to control or change the selectivity of chemical reactions. In addition, we discuss recent efforts to substitute strong reductants, such as elemental lithium and sodium, by light, and technological advances in the field

    Recyclable, bifunctional metallaphotocatalysts for C–S cross-couplings

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    Metallaphotocatalytic cross-couplings are typically carried out by combining homogeneous or heterogeneous photocatalysts with a soluble nickel complex. Attempts to realize recyclable catalytic systems use immobilized iridium complexes to harvest light. We present bifunctional, materials for metallaphotocatalytic C–S cross couplings that can be reused without losing their catalytic activity. Key to the success is the permanent immobilization of a nickel complex on the surface of a heterogeneous semiconductor through phosphonic acid anchors. The optimized catalyst harvests a broad range of the visible light spectrum and requires a nickel loading of only ~0.1 mol%

    Emerging concepts in photocatalytic organic synthesis

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    Visible light photocatalysis has become a powerful tool in organic synthesis that uses photons as traceless, sustainable reagents. Most of the activities in the field focus on the development of new reactions via common photoredox cycles, but recently a number of exciting new concepts and strategies entered less charted territories. We survey approaches that enable the use of longer wavelengths and show that the wavelength and intensity of photons are import parameters that enable tuning of the reactivity of a photocatalyst to control or change the selectivity of chemical reactions. In addition, we discuss recent efforts to substitute strong reductants, such as elemental lithium and sodium, by light and technological advances in the field

    Modulating the surface and photophysical properties of carbon dots to access colloidal photocatalysts for cross-couplings

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    Photoredox-mediated Ni-catalyzed cross-couplings are powerful transformations to form carbon–heteroatom bonds and are generally photocatalyzed by noble metal complexes. Low-cost and easy-to-prepare carbon dots (CDs) are attractive quasi-homogeneous photocatalyst alternatives, but their applicability is limited by their short photoluminescence (PL) lifetimes. By tuning the surface and PL properties of CDs, we designed colloidal CD nano-photocatalysts for a broad range of Ni-mediated cross-couplings between aryl halides and nucleophiles. In particular, a CD decorated with amino groups permitted coupling to a wide range of aryl halides and thiols under mild, base-free conditions. Mechanistic studies suggested dynamic quenching of the CD excited state by the Ni co-catalyst and identified that pyridinium iodide (pyHI), a previously used additive in metallaphotocatalyzed cross-couplings, can also act as a photocatalyst in such transformations

    Effect of Oral Semaglutide Compared With Placebo and Subcutaneous Semaglutide on Glycemic Control in Patients With Type 2 Diabetes: A Randomized Clinical Trial.

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    Importance: Glucagon-like peptide-1 (GLP-1) receptor agonists are effective therapies for the treatment of type 2 diabetes and are all currently available as an injection. Objectives: To compare the effects of oral semaglutide with placebo (primary) and open-label subcutaneous semaglutide (secondary) on glycemic control in patients with type 2 diabetes. Design, Setting, and Patients: Phase 2, randomized, parallel-group, dosage-finding, 26-week trial with 5-week follow-up at 100 sites (hospital clinics, general practices, and clinical research centers) in 14 countries conducted between December 2013 and December 2014. Of 1106 participants assessed, 632 with type 2 diabetes and insufficient glycemic control using diet and exercise alone or a stable dose of metformin were randomized. Randomization was stratified by metformin use. Interventions: Once-daily oral semaglutide of 2.5 mg (n = 70), 5 mg (n = 70), 10 mg (n = 70), 20 mg (n = 70), 40-mg 4-week dose escalation (standard escalation; n = 71), 40-mg 8-week dose escalation (slow escalation; n = 70), 40-mg 2-week dose escalation (fast escalation, n = 70), oral placebo (n = 71; double-blind) or once-weekly subcutaneous semaglutide of 1.0 mg (n = 70) for 26 weeks. Main Outcomes and Measures: The primary end point was change in hemoglobin A1c (HbA1c) from baseline to week 26. Secondary end points included change from baseline in body weight and adverse events. Results: Baseline characteristics were comparable across treatment groups. Of the 632 randomized patients (mean age, 57.1 years [SD, 10.6]; men, 395 (62.7%); diabetes duration, 6.3 years [SD, 5.2]; body weight, 92.3 kg [SD, 16.8]; BMI, 31.7 [SD, 4.3]), 583 (92%) completed the trial. Mean change in HbA1c level from baseline to week 26 decreased with oral semaglutide (dosage-dependent range, -0.7% to -1.9%) and subcutaneous semaglutide (-1.9%) and placebo (-0.3%); oral semaglutide reductions were significant vs placebo (dosage-dependent estimated treatment difference [ETD] range for oral semaglutide vs placebo, -0.4% to -1.6%; P = .01 for 2.5 mg, Conclusions and Relevance: Among patients with type 2 diabetes, oral semaglutide resulted in better glycemic control than placebo over 26 weeks. These findings support phase 3 studies to assess longer-term and clinical outcomes, as well as safety. Trial Registration: clinicaltrials.gov Identifier: NCT01923181
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