Marking Drosophila suzukii (Diptera : Drosophilidae) with fluorescent dusts

The marking of Drosophila suzukii can be an important instrument for studying the ecology and behaviour of this economically important fruit pest, aiding the development of new Integrated Pest Management (IPM) tools or strategies. There is, however, a need for a cost-effective methodology that provides an easily detectable and stable mark. Whereas fluorescent pigment powders are often used in entomological research, the pigments (series, dyes), application techniques, or doses need to be evaluated for each studied species in terms of their efficacy and possible adverse effects on the performance of the insect. The effectiveness of different application techniques and dyes (RadGlo® TP-series) and their effect on the survival of adult D. suzukii were investigated in the laboratory. Furthermore, the influence of the marking on the behaviour of the flies was examined in laboratory trap assays (olfaction) and a field recapture study (general orientation). The persistence and detectability of the marks was evaluated both on living flies (for different application techniques) and dead flies under trapping/storage conditions. The use of fluorescent powders to mark D. suzukii flies yielded a clearly detectable and highly persistent mark, without any adverse effects on the survival and behaviour of the flies

Olfactory preference of Drosophila suzukii shifts between fruit and fermentation cues over the season : effects of physiological status

Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV baited traps indeed provide a distorted image of the D. suzukii population dynamics as it is possible to capture higher numbers during this "low capture period" with synthetic lures. It was hypothesised that the preference of D. suzukii populations for fermentation cues like ACV is most pronounced during autumn, winter and spring, while the flies prefer fresh fruit cues during summer and that this seasonal preference is related to the changing physiology of the flies over the season. To test this hypothesis, the preference between fermentation cues (ACV) and host fruits (strawberries) and the effect of physiology (sex, seasonal morphology and feeding, mating and reproductive status) was investigated both in olfactometer laboratory experiments and a year-round field preference experiment. In olfactometer experiments we demonstrated that protein deprived females, virgin females with a full complement of unfertilised eggs and males show a strong preference for fermentation cues while fully fed reproductive summer morph females generally prefer fruit cues. These findings indicate that D. suzukii is attracted to fermentation volatiles in search of (protein-rich) food and to fruit volatiles in search of oviposition substrates. Winter morph and starved females displayed indiscriminating olfactory behaviour. In the field preference experiment, the hypothesised seasonal shift between fermentation and fruit cues was confirmed. This shift appeared to be highly temperature-related and was similarly observed for summer and winter morphs

Confinement Effects in Lewis Acid-Catalyzed Sugar Conversion: Steering Toward Functional Polyester Building Blocks

We report the use of solid Lewis acid catalysts for the conversion of tetrose sugars to four-carbon α-hydroxy acid esters (C_4-AHA), which are useful as functional polyester building blocks. Sn-β was by far the most active and selective catalyst, yielding up to 80% methyl vinyl glycolate (MVG), methyl-4-methoxy-2-hydroxybutanoate (MMHB), and α-hydroxy-γ-butyrolactone (HBL) combined at 95% conversion. A very high turnover frequency (TOF) of 330 mol_(C4-AHA) mol_(Sn) h^(–1) was attained using Sn-β, a more than 6-fold increase compared with homogeneous SnCl_4·5H_2O. It is shown that, using different Sn-based catalysts with various pore sizes, the product distribution is strongly dependent on the size of the catalyst pores. Catalysts containing mainly mesopores, such as Sn-MCM-41 or Sn-SBA-15, prefer the production of the more bulky MMHB, whereas microporous catalysts such as Sn-β or Sn-MFI favor the production of MVG. This effect can be further enhanced by increasing the reaction temperature. At 363 K, only 20% MVG is attained using Sn-β, but at 433 K, this increases to 50%. Using a kinetic analysis, it was found that, in microporous catalysts, steric hindrance near the Sn active site in the catalyst pores plays a dominant role in favoring the reaction pathway toward MVG. Moreover, the selectivity toward both products is kinetically controlled

Search for supersymmetry in proton-proton collisions at 13 TeV using identified top quarks

A search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks, no leptons, and an imbalance p(T)(miss) in transverse momentum. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb(-1). Search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the p(T)(miss) , the scalar sum of jet transverse momenta, and themT2 mass variable. No statistically significant excess of events is observed relative to the expectation from the standard model. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeVand neutralino masses up to 430 GeVare excluded. For amodel with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeVand neutralino masses up to 1150 GeVare excluded. These limits extend previous results.Peer reviewe

Pseudorapidity distributions of charged hadrons in proton-lead collisions at root s(NN)=5:02 and 8.16 TeV

The pseudorapidity distributions of charged hadrons in proton-lead collisions at nucleon-nucleon center-of-mass energies root s(NN) = 5.02 and 8.16 TeV are presented. The measurements are based on data samples collected by the CMS experiment at the LHC. The number of primary charged hadrons produced in non-single-diffractive proton-lead collisions is determined in the pseudorapidity range vertical bar eta(lab)vertical bar vertical bar(vertical bar eta cm vertical bar) <0.5 are 17.1 +/- 0.01 (stat) +/- 0.59 (syst) and 20.10 +/- 0.01 (stat) +/- 0.5(syst) at root s(NN) = 5.02 and 8.16 TeV, respectively. The particle densities per participant nucleon are compared to similar measurements in proton-proton, proton-nucleus, and nucleus-nucleus collisions.Peer reviewe

Observation of Top Quark Production in Proton-Nucleus Collisions

Peer reviewe

Catalytic processes for bio-based polyester building blocks

The development and introduction of synthetic plastics into the economy in the early 1900’s has significantly increased the standards of living worldwide. Many traditional materials such as wood, stone, metal and glass could suddenly be replaced by cheap, versatile polymers derived from copious petroleum reserves. Approximately one century later, scientists and researchers are now exploring more durable alternatives, such as bio-based and/or biodegradable plastics, in an effort to reduce the negative environmental impact that is associated to the production and consumption of oil-based plastics, such as contributing to climate change and pollution. The most well-established bio-based polymer on the market today is polylactic acid (PLA). Currently, this promising plastic represents less than 0.1% of the global amount of plastics produced. To increase PLA’s market share, there is a fueling demand for more cost-competitive production routes and functional (co-)polymers for high-value or high-performance applications. In the past decade, significant efforts have been devoted to develop new, catalytic routes towards PLA’s building block, lactic acid, as an alternative to its conventional, but expensive fermentative production. In contrast, less studies have focused on the conversion of lactic acid to lactide, the actual precursor for commodity PLA, despite that this step comprises approx. 30% of PLA’s total production cost. In this doctoral work, a new process was developed for lactide production by a catalytic gas-phase transesterification of alkyl lactates. Compared to the state of the art, this process is the first continuous process reported that does not require solvents or diluted lactic acid solutions, but merely a pure feedstock of alkyl lactates. In gas-phase processes, the use of alkyl lactates instead of lactic acid is advantageous, since the esters are more volatile than lactic acid, they do not polymerize spontaneously in concentrated solutions and they do not have an acid group which might catalyze unwanted side-reactions. Moreover, alkyl lactates are intermediates during lactic acid purification and can be produced by emerging catalytic routes. With this process, an unprecedented lactide productivity can be achieved compared to other, lactic acid-based gas-phase processes. Supported TiO2/SiO2 catalysts were selected from a broad screening as materials of choice for catalyzing the cyclization of alkyl lactates. The reaction conditions were optimized to maximize lactide yield and/or productivity, in accordance to the underlying thermodynamics. From extensive characterization of various Ti-Si catalysts, it was elucidated that covalent Ti-O-Si bonds between the Ti active sites and the Si-support are required in order to be catalytically active and selective towards lactide, irrespective of the catalyst structure, topology or morphology. Through DR UV-VIS spectroscopy, it was found that isolated tetrahedral TiO4 sites are more active than five-fold TiO5 or octahedral TiO6 sites, and the former culminate at high Ti-dispersions. Hence, lactide productivity was optimized by balancing the amount of active sites on the catalyst and the specific catalytic activity of each site. High-surface SiO2 supports (e.g. MCM-41) provided the largest surface area and hence, a greater Ti-dispersion, even at higher loadings of Ti. The highest lactide productivity was therefore obtained with a TiO2/MCM-41 catalyst. The catalytic production of lactide in gas-phase is flexible on the alkyl lactates used. No significant thermodynamic differences were observed, but the reactivity of the esters is correlated to the basicity of the leaving alcohol group, and generally decreases in the order of methyl > ethyl ≈ n-butyl > isopropyl lactate. Moreover, the same process can be expanded towards the production of other cyclic esters as well, such as glycolide from methyl glycolate. In a separate chapter of this doctoral thesis, we also explored the catalytic production of functional, lactic acid-like C4-esters, viz. methyl vinyl glycolate (MVG) and methyl-4-methoxy-2-hydroxybutanoate (MMHB) from tetrose sugars. Of these, MVG in particular is considered a suitable building block for functionalizable, high-value PLA polymers or a platform molecule for other high-end chemicals. The selectivity towards both products highly depends on the pore size of the heterogeneous Sn-catalyst and reaction temperature. Confinement effects inside the pores of Sn-zeolites lead to an increased selectivity towards MVG, especially at higher reaction temperatures. Development of such catalytic routes towards functionalizable polyester building blocks paves the way towards high-value PLA, whereas the new ester-based gas phase process for lactide production could reduce production costs of commodity PLA.nrpages: 167status: publishe

Tin triflate-catalyzed conversion of cellulose to valuable (alpha-hydroxy-) esters

© 2016 Elsevier B.V. The direct conversion of cellulose with metal-triflate catalysts in methanol is investigated. SnII-triflate remarkably catalyzes the formation of a mixture of useful α-hydroxy esters such as methyl lactate, methyl vinyl glycolate and methyl-4-methoxy-2-hydroxybutanoate, on top of methyl levulinate. Compared to other metal triflates or Sn salts, the catalytic features of SnII-triflate are distinct and linked to the interplay between its Brønsted and Lewis acidic component. A total ester yield (carbon-based, mol%) in the 60%-range could be obtained from cellulose after 2 h at 200 °C for cellulose loadings up to 20 g L−1 with 4.8 mM of catalyst. The cascade reaction network, confirmed by feeding intermediates, highlights the importance of a fast retro-aldol of the hexose intermediates – opposed to their dehydration – when α-hydroxy esters are targeted. By manipulating the triflate-to-Sn ratio, nearly 40% of α-hydroxy esters can be produced in a one-pot approach. Such mixtures could help fuel the demand for functional biodegradable polyesters.publisher: Elsevier articletitle: Tin triflate-catalyzed conversion of cellulose to valuable (α-hydroxy-) esters journaltitle: Catalysis Today articlelink: http://dx.doi.org/10.1016/j.cattod.2016.01.035 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe

Catalytic Gas‐Phase Cyclization of Glycolate Esters: a Novel Route Toward Glycolide‐Based Bioplastics

A catalytic process to produce glycolide, the cyclic dimer of glycolic acid (GA), is proposed. Glycolide is the key building block of the biodegradable plastic polyglycolic acid. Instead of the current industrial two‐step route, which involves the polycondensation of GA and a subsequent backbiting reaction, a new route based on the gas‐phase transesterification of methyl glycolate (MGA) over a fixed catalyst bed is presented. With specific supported TiO2 catalysts, a high glycolide selectivity of 75‐78% can be achieved at the thermodynamically‐limited equilibrium conversion of MGA (54% at 300°C, 5.6vol% MGA). The absence of solvent and the continuous nature of the process should allow for easy product separation and recycling of unconverted esters, while the few side‐products, i.e. linear alkyl glycolate dimers and trimers seem recoverable via methanolysis. The reaction is compared to the cyclization of other α‐hydroxy esters, such as methyl lactate to lactide, over the same catalysts, in terms of kinetics and thermodynamics. The absence of a methyl substitution on the α‐carbon seems to lead to faster cyclization kinetics of MGA when compared to methyl lactate or the double‐substituted methyl‐2‐hydroxy‐isobutyrate. Contrarily, glycolide production is less favored thermodynamically compared to lactide. The absence of glycolide decomposition at temperatures up to 300°C however allows to increase equilibrium conversion by taking the endergonic reaction to higher temperatures.status: publishe