Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Impact of maternal body mass index and gestational weight gain on pregnancy complications: an individual participant data meta-analysis of European, North American and Australian cohorts
    Santos, S. ; Voerman, E. ; Amiano, P. ; Barros, H. ; Beilin, L.J. ; Bergström, A. ; Charles, M.A. ; Chatzi, L. ; Chevrier, C. ; Chrousos, G.P. ; Corpeleijn, E. ; Costa, O. ; Costet, N. ; Crozier, S. ; Devereux, G. ; Doyon, M. ; Eggesbø, M. ; Fantini, M.P. ; Farchi, S. ; Forastiere, F. ; Georgiu, V. ; Godfrey, K.M. ; Gori, D. ; Grote, V. ; Hanke, W. ; Hertz-Picciotto, I. ; Heude, B. ; Hivert, M.F. ; Hryhorczuk, D. ; Huang, R.C. ; Inskip, H. ; Karvonen, A.M. ; Kenny, L.C. ; Koletzko, B. ; Küpers, L.K. ; Lagström, H. ; Lehmann, I. ; Magnus, P. ; Majewska, R. ; Mäkelä, J. ; Manios, Y. ; McAuliffe, F.M. ; McDonald, S.W. ; Mehegan, J. ; Melén, E. ; Mommers, M. ; Morgen, C.S. ; Moschonis, G. ; Murray, D. ; Ní Chaoimh, C. ; Nohr, E.A. ; Nybo Andersen, A.M. ; Oken, E. ; Oostvogels, A.J.J.M. ; Pac, A. ; Papadopoulou, E. ; Pekkanen, J. ; Pizzi, C. ; Polanska, K. ; Porta, D. ; Richiardi, L. ; Rifas-Shiman, S.L. ; Roeleveld, N. ; Ronfani, L. ; Santos, A.C. ; Standl, M. ; Stigum, H. ; Stoltenberg, C. ; Thiering, E. ; Thijs, C. ; Torrent, M. ; Tough, S.C. ; Trnovec, T. ; Turner, S. ; Gelder, M.M.H.J. van; Rossem, L. van; Berg, A. von; Vrijheid, M. ; Vrijkotte, T.G.M. ; West, J. ; Wijga, A.H. ; Wright, J. ; Zvinchuk, O. ; Sørensen, T.I.A. ; Lawlor, D.A. ; Gaillard, R. ; Jaddoe, V.W.V. - \ 2019
    BJOG : an international journal of obstetrics and gynaecology 126 (2019)8. - ISSN 1470-0328 - p. 984 - 995.
    Birthweight - body mass index - pregnancy complications - preterm birth - weight gain

    Objective: To assess the separate and combined associations of maternal pre-pregnancy body mass index (BMI) and gestational weight gain with the risks of pregnancy complications and their population impact. Design: Individual participant data meta-analysis of 39 cohorts. Setting: Europe, North America, and Oceania. Population: 265 270 births. Methods: Information on maternal pre-pregnancy BMI, gestational weight gain, and pregnancy complications was obtained. Multilevel binary logistic regression models were used. Main outcome measures: Gestational hypertension, pre-eclampsia, gestational diabetes, preterm birth, small and large for gestational age at birth. Results: Higher maternal pre-pregnancy BMI and gestational weight gain were, across their full ranges, associated with higher risks of gestational hypertensive disorders, gestational diabetes, and large for gestational age at birth. Preterm birth risk was higher at lower and higher BMI and weight gain. Compared with normal weight mothers with medium gestational weight gain, obese mothers with high gestational weight gain had the highest risk of any pregnancy complication (odds ratio 2.51, 95% CI 2.31– 2.74). We estimated that 23.9% of any pregnancy complication was attributable to maternal overweight/obesity and 31.6% of large for gestational age infants was attributable to excessive gestational weight gain. Conclusions: Maternal pre-pregnancy BMI and gestational weight gain are, across their full ranges, associated with risks of pregnancy complications. Obese mothers with high gestational weight gain are at the highest risk of pregnancy complications. Promoting a healthy pre-pregnancy BMI and gestational weight gain may reduce the burden of pregnancy complications and ultimately the risk of maternal and neonatal morbidity. Tweetable abstract: Promoting a healthy body mass index and gestational weight gain might reduce the population burden of pregnancy complications.

    New records and updated checklist of mosquitoes (Diptera: Culicidae) from Lao People's Democratic Republic, with special emphasis on adult and larval surveillance in Khammuane Province
    Motoki, Maysa T. ; Vongphayloth, Khamsing ; Rueda, Leopoldo M. ; Miot, Elliott F. ; Hiscox, Alexandra ; Hertz, Jeffrey C. ; Brey, Paul T. - \ 2019
    Journal of Vector Ecology 44 (2019)1. - ISSN 1081-1710 - p. 76 - 88.
    Culicidae - DNA barcode - Khammuane Province - Lao PDR - mosquito species list - mosquito surveillance

    A list of mosquitoes from the Nakai Nam Theun National Protected Area along the Nam Theun, Nam Mon, Nam Noy, and Nam On rivers, Nakai District, Khammuane Province, Lao People's Democratic Republic (Lao PDR) is presented. Fifty-four mosquito taxa were identified, including 15 new records in the Lao PDR. A fragment of the mtDNA cytochrome c oxidase subunit I (COI) gene, barcode region, was generated for 34 specimens, and together with four specimens already published, it represented 23 species in eight genera. In addition, an updated checklist of 170 mosquito taxa from Lao PDR is provided based on field collections from Khammuane Province, the literature, and specimens deposited in the Smithsonian Institution, National Museum of Natural History (SI-NMNH), Washington, DC, U.S.A. This paper provides additional information about the biodiversity of mosquito fauna in Lao PDR.

    Association of Gestational Weight Gain With Adverse Maternal and Infant Outcomes
    Voerman, Ellis ; Santos, Susana ; Inskip, Hazel ; Amiano, Pilar ; Barros, Henrique ; Charles, Marie Aline ; Chatzi, Leda ; Chrousos, George P. ; Corpeleijn, Eva ; Crozier, Sarah ; Doyon, Myriam ; Eggesbø, Merete ; Fantini, Maria Pia ; Farchi, Sara ; Forastiere, Francesco ; Georgiu, Vagelis ; Gori, Davide ; Hanke, Wojciech ; Hertz-Picciotto, Irva ; Heude, Barbara ; Hivert, Marie France ; Hryhorczuk, Daniel ; Iñiguez, Carmen ; Karvonen, Anne M. ; Küpers, Leanne K. ; Lagström, Hanna ; Lawlor, Debbie A. ; Lehmann, Irina ; Magnus, Per ; Majewska, Renata ; Mäkelä, Johanna ; Manios, Yannis ; Mommers, Monique ; Morgen, Camilla S. ; Moschonis, George ; Nohr, Ellen A. ; Nybo Andersen, Anne Marie ; Oken, Emily ; Pac, Agnieszka ; Papadopoulou, Eleni ; Pekkanen, Juha ; Pizzi, Costanza ; Polanska, Kinga ; Porta, Daniela ; Richiardi, Lorenzo ; Rifas-Shiman, Sheryl L. ; Roeleveld, Nel ; Ronfani, Luca ; Santos, Ana C. ; Standl, Marie - \ 2019
    JAMA: The Journal of the American Medical Association 321 (2019)17. - ISSN 0098-7484 - p. 1702 - 1715.

    Importance: Both low and high gestational weight gain have been associated with adverse maternal and infant outcomes, but optimal gestational weight gain remains uncertain and not well defined for all prepregnancy weight ranges. Objectives: To examine the association of ranges of gestational weight gain with risk of adverse maternal and infant outcomes and estimate optimal gestational weight gain ranges across prepregnancy body mass index categories. Design, Setting, and Participants: Individual participant-level meta-analysis using data from 196 670 participants within 25 cohort studies from Europe and North America (main study sample). Optimal gestational weight gain ranges were estimated for each prepregnancy body mass index (BMI) category by selecting the range of gestational weight gain that was associated with lower risk for any adverse outcome. Individual participant-level data from 3505 participants within 4 separate hospital-based cohorts were used as a validation sample. Data were collected between 1989 and 2015. The final date of follow-up was December 2015. Exposures: Gestational weight gain. Main Outcomes and Measures: The main outcome termed any adverse outcome was defined as the presence of 1 or more of the following outcomes: preeclampsia, gestational hypertension, gestational diabetes, cesarean delivery, preterm birth, and small or large size for gestational age at birth. Results: Of the 196 670 women (median age, 30.0 years [quartile 1 and 3, 27.0 and 33.0 years] and 40 937 were white) included in the main sample, 7809 (4.0%) were categorized at baseline as underweight (BMI <18.5); 133 788 (68.0%), normal weight (BMI, 18.5-24.9); 38 828 (19.7%), overweight (BMI, 25.0-29.9); 11 992 (6.1%), obesity grade 1 (BMI, 30.0-34.9); 3284 (1.7%), obesity grade 2 (BMI, 35.0-39.9); and 969 (0.5%), obesity grade 3 (BMI, ≥40.0). Overall, any adverse outcome occurred in 37.2% (n = 73 161) of women, ranging from 34.7% (2706 of 7809) among women categorized as underweight to 61.1% (592 of 969) among women categorized as obesity grade 3. Optimal gestational weight gain ranges were 14.0 kg to less than 16.0 kg for women categorized as underweight; 10.0 kg to less than 18.0 kg for normal weight; 2.0 kg to less than 16.0 kg for overweight; 2.0 kg to less than 6.0 kg for obesity grade 1; weight loss or gain of 0 kg to less than 4.0 kg for obesity grade 2; and weight gain of 0 kg to less than 6.0 kg for obesity grade 3. These gestational weight gain ranges were associated with low to moderate discrimination between those with and those without adverse outcomes (range for area under the receiver operating characteristic curve, 0.55-0.76). Results for discriminative performance in the validation sample were similar to the corresponding results in the main study sample (range for area under the receiver operating characteristic curve, 0.51-0.79). Conclusions and Relevance: In this meta-analysis of pooled individual participant data from 25 cohort studies, the risk for adverse maternal and infant outcomes varied by gestational weight gain and across the range of prepregnancy weights. The estimates of optimal gestational weight gain may inform prenatal counseling; however, the optimal gestational weight gain ranges had limited predictive value for the outcomes assessed.

    Meta-analysis of epigenome-wide association studies in neonates reveals widespread differential DNA methylation associated with birthweight
    Küpers, Leanne K. ; Monnereau, Claire ; Sharp, Gemma C. ; Yousefi, Paul ; Salas, Lucas A. ; Ghantous, Akram ; Page, Christian M. ; Reese, Sarah E. ; Wilcox, Allen J. ; Czamara, Darina ; Starling, Anne P. ; Novoloaca, Alexei ; Lent, Samantha ; Roy, Ritu ; Hoyo, Cathrine ; Breton, Carrie V. ; Allard, Catherine ; Just, Allan C. ; Bakulski, Kelly M. ; Holloway, John W. ; Everson, Todd M. ; Xu, Cheng Jian ; Huang, Rae Chi ; Plaat, Diana A. van der; Wielscher, Matthias ; Merid, Simon Kebede ; Ullemar, Vilhelmina ; Rezwan, Faisal I. ; Lahti, Jari ; Dongen, Jenny van; Langie, Sabine A.S. ; Richardson, Tom G. ; Magnus, Maria C. ; Nohr, Ellen A. ; Xu, Zongli ; Duijts, Liesbeth ; Zhao, Shanshan ; Zhang, Weiming ; Plusquin, Michelle ; DeMeo, Dawn L. ; Solomon, Olivia ; Heimovaara, Joosje H. ; Jima, Dereje D. ; Gao, Lu ; Bustamante, Mariona ; Perron, Patrice ; Wright, Robert O. ; Hertz-Picciotto, Irva ; Zhang, Hongmei ; Karagas, Margaret R. ; Gehring, Ulrike ; Marsit, Carmen J. ; Beilin, Lawrence J. ; Vonk, Judith M. ; Jarvelin, Marjo Riitta ; Bergström, Anna ; Örtqvist, Anne K. ; Ewart, Susan ; Villa, Pia M. ; Moore, Sophie E. ; Willemsen, Gonneke ; Standaert, Arnout R.L. ; Håberg, Siri E. ; Sørensen, Thorkild I.A. ; Taylor, Jack A. ; Räikkönen, Katri ; Yang, Ivana V. ; Kechris, Katerina ; Nawrot, Tim S. ; Silver, Matt J. ; Gong, Yun Yun ; Richiardi, Lorenzo ; Kogevinas, Manolis ; Litonjua, Augusto A. ; Eskenazi, Brenda ; Huen, Karen ; Mbarek, Hamdi ; Maguire, Rachel L. ; Dwyer, Terence ; Vrijheid, Martine ; Bouchard, Luigi ; Baccarelli, Andrea A. ; Croen, Lisa A. ; Karmaus, Wilfried ; Anderson, Denise ; Vries, Maaike de; Sebert, Sylvain ; Kere, Juha ; Karlsson, Robert ; Arshad, Syed Hasan ; Hämäläinen, Esa ; Routledge, Michael N. ; Boomsma, Dorret I. ; Feinberg, Andrew P. ; Newschaffer, Craig J. ; Govarts, Eva ; Moisse, Matthieu ; Fallin, M.D. ; Melén, Erik ; Prentice, Andrew M. ; Kajantie, Eero ; Almqvist, Catarina ; Oken, Emily ; Dabelea, Dana ; Boezen, H.M. ; Melton, Phillip E. ; Wright, Rosalind J. ; Koppelman, Gerard H. ; Trevisi, Letizia ; Hivert, Marie France ; Sunyer, Jordi ; Munthe-Kaas, Monica C. ; Murphy, Susan K. ; Corpeleijn, Eva ; Wiemels, Joseph ; Holland, Nina ; Herceg, Zdenko ; Binder, Elisabeth B. ; Davey Smith, George ; Jaddoe, Vincent W.V. ; Lie, Rolv T. ; Nystad, Wenche ; London, Stephanie J. ; Lawlor, Debbie A. ; Relton, Caroline L. ; Snieder, Harold ; Felix, Janine F. - \ 2019
    Nature Communications 10 (2019)1. - ISSN 2041-1723

    Birthweight is associated with health outcomes across the life course, DNA methylation may be an underlying mechanism. In this meta-analysis of epigenome-wide association studies of 8,825 neonates from 24 birth cohorts in the Pregnancy And Childhood Epigenetics Consortium, we find that DNA methylation in neonatal blood is associated with birthweight at 914 sites, with a difference in birthweight ranging from −183 to 178 grams per 10% increase in methylation (P Bonferroni < 1.06 x 10 −7 ). In additional analyses in 7,278 participants, <1.3% of birthweight-associated differential methylation is also observed in childhood and adolescence, but not adulthood. Birthweight-related CpGs overlap with some Bonferroni-significant CpGs that were previously reported to be related to maternal smoking (55/914, p = 6.12 x 10 −74 ) and BMI in pregnancy (3/914, p = 1.13x10 −3 ), but not with those related to folate levels in pregnancy. Whether the associations that we observe are causal or explained by confounding or fetal growth influencing DNA methylation (i.e. reverse causality) requires further research.

    Maternal body mass index, gestational weight gain, and the risk of overweight and obesity across childhood : An individual participant data meta-analysis
    Voerman, Ellis ; Santos, Susana ; Patro Golab, Bernadeta ; Amiano, Pilar ; Ballester, Ferran ; Barros, Henrique ; Bergström, Anna ; Charles, Marie Aline ; Chatzi, Leda ; Chevrier, Cécile ; Chrousos, George P. ; Corpeleijn, Eva ; Costet, Nathalie ; Crozier, Sarah ; Devereux, Graham ; Eggesbø, Merete ; Ekström, Sandra ; Fantini, Maria Pia ; Farchi, Sara ; Forastiere, Francesco ; Georgiu, Vagelis ; Godfrey, Keith M. ; Gori, Davide ; Grote, Veit ; Hanke, Wojciech ; Hertz-Picciotto, Irva ; Heude, Barbara ; Hryhorczuk, Daniel ; Huang, Rae Chi ; Inskip, Hazel ; Iszatt, Nina ; Karvonen, Anne M. ; Kenny, Louise C. ; Koletzko, Berthold ; Küpers, Leanne K. ; Lagström, Hanna ; Lehmann, Irina ; Magnus, Per ; Majewska, Renata ; Mäkelä, Johanna ; Manios, Yannis ; McAuliffe, Fionnuala M. ; McDonald, Sheila W. ; Mehegan, John ; Mommers, Monique ; Morgen, Camilla S. ; Mori, Trevor A. ; Moschonis, George ; Murray, Deirdre ; Chaoimh, Carol Ní ; Nohr, Ellen A. ; Nybo Andersen, Anne Marie ; Oken, Emily ; Oostvogels, Adriëtte J.J.M. ; Pac, Agnieszka ; Papadopoulou, Eleni ; Pekkanen, Juha ; Pizzi, Costanza ; Polanska, Kinga ; Porta, Daniela ; Richiardi, Lorenzo ; Rifas-Shiman, Sheryl L. ; Ronfani, Luca ; Santos, Ana C. ; Standl, Marie ; Stoltenberg, Camilla ; Thiering, Elisabeth ; Thijs, Carel ; Torrent, Maties ; Tough, Suzanne C. ; Trnovec, Tomas ; Turner, Steve ; Rossem, Lenie van; Berg, Andrea von; Vrijheid, Martine ; Vrijkotte, Tanja G.M. ; West, Jane ; Wijga, Alet ; Wright, John ; Zvinchuk, Oleksandr ; Sørensen, Thorkild I.A. ; Lawlor, Debbie A. ; Gaillard, Romy ; Jaddoe, Vincent W.V. - \ 2019
    PLOS Medicine 16 (2019)2. - ISSN 1549-1676 - p. e1002744 - e1002744.

    BACKGROUND: Maternal obesity and excessive gestational weight gain may have persistent effects on offspring fat development. However, it remains unclear whether these effects differ by severity of obesity, and whether these effects are restricted to the extremes of maternal body mass index (BMI) and gestational weight gain. We aimed to assess the separate and combined associations of maternal BMI and gestational weight gain with the risk of overweight/obesity throughout childhood, and their population impact. METHODS AND FINDINGS: We conducted an individual participant data meta-analysis of data from 162,129 mothers and their children from 37 pregnancy and birth cohort studies from Europe, North America, and Australia. We assessed the individual and combined associations of maternal pre-pregnancy BMI and gestational weight gain, both in clinical categories and across their full ranges, with the risks of overweight/obesity in early (2.0-5.0 years), mid (5.0-10.0 years) and late childhood (10.0-18.0 years), using multilevel binary logistic regression models with a random intercept at cohort level adjusted for maternal sociodemographic and lifestyle-related characteristics. We observed that higher maternal pre-pregnancy BMI and gestational weight gain both in clinical categories and across their full ranges were associated with higher risks of childhood overweight/obesity, with the strongest effects in late childhood (odds ratios [ORs] for overweight/obesity in early, mid, and late childhood, respectively: OR 1.66 [95% CI: 1.56, 1.78], OR 1.91 [95% CI: 1.85, 1.98], and OR 2.28 [95% CI: 2.08, 2.50] for maternal overweight; OR 2.43 [95% CI: 2.24, 2.64], OR 3.12 [95% CI: 2.98, 3.27], and OR 4.47 [95% CI: 3.99, 5.23] for maternal obesity; and OR 1.39 [95% CI: 1.30, 1.49], OR 1.55 [95% CI: 1.49, 1.60], and OR 1.72 [95% CI: 1.56, 1.91] for excessive gestational weight gain). The proportions of childhood overweight/obesity prevalence attributable to maternal overweight, maternal obesity, and excessive gestational weight gain ranged from 10.2% to 21.6%. Relative to the effect of maternal BMI, excessive gestational weight gain only slightly increased the risk of childhood overweight/obesity within each clinical BMI category (p-values for interactions of maternal BMI with gestational weight gain: p = 0.038, p < 0.001, and p = 0.637 in early, mid, and late childhood, respectively). Limitations of this study include the self-report of maternal BMI and gestational weight gain for some of the cohorts, and the potential of residual confounding. Also, as this study only included participants from Europe, North America, and Australia, results need to be interpreted with caution with respect to other populations. CONCLUSIONS: In this study, higher maternal pre-pregnancy BMI and gestational weight gain were associated with an increased risk of childhood overweight/obesity, with the strongest effects at later ages. The additional effect of gestational weight gain in women who are overweight or obese before pregnancy is small. Given the large population impact, future intervention trials aiming to reduce the prevalence of childhood overweight and obesity should focus on maternal weight status before pregnancy, in addition to weight gain during pregnancy.

    Comparative microbiome analysis of a Fusarium wilt suppressive soil and a Fusarium wilt conducive soil from the Châteaurenard region
    Siegel-Hertz, Katarzyna ; Edel-Hermann, Véronique ; Chapelle, Emilie ; Terrat, Sébastien ; Raaijmakers, Jos M. ; Steinberg, Christian - \ 2018
    Frontiers in Microbiology 9 (2018)APR. - ISSN 1664-302X
    454 pyrosequencing - Bacterial community - Biocontrol agent - Diversity - Fungal community - Metabarcoding
    Disease-suppressive soils are soils in which specific soil-borne plant pathogens cause only limited disease although the pathogen and susceptible host plants are both present. Suppressiveness is in most cases of microbial origin. We conducted a comparative metabarcoding analysis of the taxonomic diversity of fungal and bacterial communities from suppressive and non-suppressive (conducive) soils as regards Fusarium wilts sampled from the Châteaurenard region (France). Bioassays based on Fusarium wilt of flax confirmed that disease incidence was significantly lower in the suppressive soil than in the conducive soil. Furthermore, we succeeded in partly transferring Fusarium wilt-suppressiveness to the conducive soil by mixing 10% (w/w) of the suppressive soil into the conducive soil. Fungal diversity differed significantly between the suppressive and conducive soils. Among dominant fungal operational taxonomic units (OTUs) affiliated to known genera, 17 OTUs were detected exclusively in the suppressive soil. These OTUs were assigned to the Acremonium, Chaetomium, Cladosporium, Clonostachys, Fusarium, Ceratobasidium, Mortierella, Penicillium, Scytalidium, and Verticillium genera. Additionally, the relative abundance of specific members of the bacterial community was significantly higher in the suppressive and mixed soils than in the conducive soil. OTUs found more abundant in Fusarium wilt-suppressive soils were affiliated to the bacterial genera Adhaeribacter, Massilia, Microvirga, Rhizobium, Rhizobacter, Arthrobacter, Amycolatopsis, Rubrobacter, Paenibacillus, Stenotrophomonas, and Geobacter. Several of the fungal and bacterial genera detected exclusively or more abundantly in the Fusarium wilt-suppressive soil included genera known for their activity against F. oxysporum. Overall, this study supports the potential role of known fungal and bacterial genera in Fusarium wilt suppressive soils from Châteaurenard and pinpoints new bacterial and fungal genera for their putative role in Fusarium wilt suppressiveness.
    PowerPoint Slides as Speaking Notes: The Influence of Speaking Anxiety on the Use of Text on Slides
    Woerkum, C.M.J. van; Hertz, B. ; Kerkhof, P. - \ 2016
    Business and Professional Communication Quarterly 79 (2016)3. - ISSN 2329-4906 - p. 348 - 359.
    PowerPoint presentations are often criticized for the excessive use of text on the
    slides. In a study of 97 academic scholars, we found that presenters indeed used
    substantially more text than is advised. Speaking anxiety was found to be related to
    the time spent on preparing and rehearsing, and time spent on rehearsing is related
    to the number of words on the slides. Anxious presenters appear to use PowerPoint
    slides as speaking notes. Presenters should be trained to overcome their speaking
    anxiety by means other than the abundant use of words on their slides.
    Why do scholars use PowerPoint the way they do?
    Hertz, Brigitte ; Woerkum, Cees van; Kerkhof, Peter - \ 2015
    Business Communication Quarterly 78 (2015)3. - ISSN 1080-5699 - p. 273 - 291.
    PowerPoint - Presentations - Scholars - Teaching communication

    PowerPoint has received much criticism regarding excessive use of text and the lack of contact with the audience. Why presenters use PowerPoint in this way has not been studied so far. Our study using interviews with beginning and advanced presenters shows that some use the program as a speaking note and as a means to draw the attention away from themselves. Some even think that PowerPoint can replace rhetorical skills. Slides are mainly designed on the basis of commonsense, instead of guidelines based on human information processing. Implications for the teaching of PowerPoint use in business communication are discussed.

    Spotlight on the presenter : a study into presentations of conference papers with PowerPoint
    Hertz, B. - \ 2015
    Wageningen University. Promotor(en): Cees van Woerkum, co-promotor(en): P. Kerkhof. - Wageningen : Wageningen University - ISBN 9789462573192 - 193
    publiceren - informatieverspreiding - communicatievaardigheden - verbale communicatie - toepassingen - wetenschappers - openbare redes - publishing - diffusion of information - communication skills - verbal communication - applications - scientists - public speeches

    Abstract

    1. Introduction

    PowerPoint is the most widely used presentation software tool. As of 2012, PowerPoint had more than 200 million presenters worldwide. Presenters all over the world use the program. Some use it for university teaching, others for business meetings and some even use PowerPoint to deliver a sermon. But the program doesn’t always seem to be used to the satisfaction of the audience. In many critical articles, presenters are accused of using too many words on their slides and too often looking at the projection instead of keeping eye contact with the audience. Some authors also criticize the program itself for what they see as a negative influence on presentations.

    If these critical observations are valid, then PowerPoint presentations don’t conform to the advice given in instruction books nor to the outcome of research into human information processing. This advice usually proposes the use of minimal text on slides, and instead using pictures or other graphics. This would help the audience process the information. In addition, the instruction book stress the importance of maintaining eye contact with the audience. It is remarkable that the program is so frequently used, while it is so often criticized for what seem to be valid reasons.

    There has been some research into PowerPoint use in the classroom, investigating the effects on student appreciation and grades. Much of this research does not describe how nor why the program is used in these situations. The critical articles on PowerPoint are mainly based on personal experiences and not on research. So there has not been much empirical evidence that presenters actually do use too many words or that they look too often at the projection, nor has the influence of PowerPoint on the presentation been established. In addition it is not clear why so many presenters don’t seem to follow the advice in instruction books, which say to use a minimum amount of text on a slide and which stress the importance of maintaining eye contact with the audience.

    This dissertation focuses on the role of the presenter. It investigates how presenters use PowerPoint and if they are guilty of the negative behavior mentioned above. If they are guilty, what are the reasons they use PowerPoint in this way? Some authors have suggested that presenters use PowerPoint not only for the benefit of the audience, but that they also use the words on the slides as speaking notes. In particular, presenters suffering from speaking anxiety might be afraid of being “lost for words” or forgetting the structure of their presentation. They would then be able to turn to the text on the slides as support. This dissertation will investigate the possible role of speaking anxiety and how it affects PowerPoint usage.

    The research looks at the use of PowerPoint by scholars presenting conference papers. Conferences play a central role in the network of scientific communication and are important for a researcher’s profile. The majority of scholars present their work at conferences several times a year and these presentations can be demanding and challenging. In contrast with writing and publishing a paper, conferences allow scholars to interact with an audience of their peers who will evaluate their work by posing critical questions. Challenging exposure of this kind might well engender or increase speaking anxiety in the presenter.

    Clearly there is a need for empirical research on PowerPoint use, research focused on the program’s use in delivering scholarly presentations. Questions to be answered by the research include:

    • How do scholars use PowerPoint?

    • Why do scholars use PowerPoint in the way that they do?
    • Does speaking anxiety influence the way that scholars use PowerPoint?

    • Does PowerPoint influence the quality of presentations?

    This thesis studies the use of PowerPoint in a real life setting and looks at presentations as being complex interactions among slides, presenter behavior and audience. An overview of the different elements regarding the presenter, his/her background, the presentation, the presenter’s behavior and the PowerPoint program itself can be found in Figure I.

    2. Method

    There is a literature review and three empirical studies. The literature review compares the program with its predecessors and describes the software, slide design and the user’s presentation behavior, focusing on the interaction of these elements. Instruction books and articles on PowerPoint, criticism and empirical research on the topics of slide design, presentation behavior and its effects on audiences are discussed.

    In the first empirical study, fifteen scientific presentations of language scientists are analyzed on the use of text and pictures on the slides. The physical and verbal behavior of the presenter has also been studied, specifically investigating how often presenters look at the projection and if they verbally introduce a slide. Furthermore the relation between the slides and the presenter’s behavior has been analyzed.

    The second empirical study employs interviews with scholars about their reasons for PowerPoint use. It distinguishes between first-year PhD students (beginners) and advanced, prize winning scholars from different disciplines of science (humanities, physical science, social science and medical science). Special attention is given to the acquisition of PowerPoint skills.

    The third study consists of a survey using social scientists and focuses on the influence of speaking anxiety on the use of PowerPoint. It tests if speaking anxiety causes presenters to spend more time on preparing and rehearsing the presentation, and analyzes the possible relationships among speaking anxiety, time spent on preparing and rehearsing a presentation, and the use of words on a slide.

    3. Results

    Certain characteristics of PowerPoint such as its default-settings and the ability to use slides on the Internet and as handouts may tempt the presenter to increase the amount of text on slides. These choices, however, are not necessary, and are decisions made by the presenter. The scholars in our study used a relatively large number of words when compared to what instruction books advise (a maximum of 20 to 36 words per slide, depending on the author). An average number of 35 (language scientists) and 50 (social scientists) per slide was found. Many of the scholars used a small number of pictures (depending on the scientific discipline).

    Presenters look on average 73 times at the projection during their presentation of 20 minutes (more than three times a minute). Looking at the projection to indicate a new slide or ‘new’ elements on a slide seems to be characteristic for the use of PowerPoint. Presenters turn away from the audience and break eye-contact, something which is considered negative in making presentations. The critics of PowerPoint clearly have a point when they complain about the high number of words on the slides and about presenters looking towards the projection.

    There are differences, however, between beginning and advanced presenters. Beginners use more than twice as many words per minute than advanced presenters and only half as many pictures. In maintaining contact with the audience there is also a difference between beginning and advanced scholars. Advanced presenters often like to present without the use of PowerPoint because this allows more contact with their audience.

    Some scholars say that they use the text on the slides as speaking notes. Many have also said that they use pictures almost exclusively for the benefit of the audience. Beginners probably use more text and fewer pictures because they suffer more from speaking anxiety than advanced presenters. They might be more concerned with their own performance. Advanced scholars on the other hand have indicated that they have their audience in mind when preparing and delivering a presentation. Speaking anxiety, in an indirect way, also plays a role in the number of words used on the slides. Anxious presenters spend more time rehearsing the presentation; this is related to the number of words used on the slides.

    Scholars often seem to lack knowledge about how to use PowerPoint in an appropriate manner. Instead of receiving training in using PowerPoint, they learn to present with the program by experimenting and by observing colleagues and designing slides on the basis of common sense, which is often against the advice in instruction books. Moreover some scholars erroneously think that PowerPoint makes rhetorical skills redundant.

    4. Conclusions

    The concept of “performance” seems to be appropriate in describing all the elements that matter in the presentation itself: speech, animated slides, working with projections, physical motion and maintaining eye contact with the audience. Presenters need an understanding of how audiences process different sources of information, and they must then be able to orchestrate their presentation skills in appropriate ways. If we look at PowerPoint presentations as performances, we can see that presenters must be designers, actors and directors at the same time.

    It is clear that PowerPoint elicits behavior that is not always consistent with what is considered to be good presentation form. This, however, is not the fault of the program. The apparent user friendliness of PowerPoint might disguise the fact that presentations with the program are in fact complex. It is not PowerPoint itself which causes some bad presentations, but the choices and behavior of the presenters who must deal with all the new possibilities and requirements inherent in this program.

    Presenters should be educated in appropriate slide design. They also should be taught how to direct the attention of the audience. It is not sufficient to teach presenters how they should design and present their slides, however, if they aren’t helped to learn how to reduce their speaking anxiety in ways other than using the PowerPoint slides as support. This thesis suggests ways of teaching these skills

    Wetenschappelijke presentaties met Power-Point. Schadelijke software?
    Hertz, B. ; Woerkum, C. van; Kerkhof, P. - \ 2013
    In: Studies in taalbeheersing / Boogaart, R., Janssen, H., Assen : Van Gorcum - ISBN 9789023249917 - p. 125 - 134.
    Biochemical and functional characterization of recombinant fungal immunomodulatory proteins (rFIPs)
    Bastiaan-Net, S. ; Chanput, W. ; Hertz, A. ; Zwittink, R.D. ; Mes, J.J. ; Wichers, H.J. - \ 2013
    International Immunopharmacology 15 (2013)1. - ISSN 1567-5769 - p. 167 - 175.
    ganoderma-lucidium - murine macrophages - fip-fve - expression - lectins - cloning - gene - lz-8 - mushroom - sinense
    In this study two novel FIPs have been identified and characterized. The first is FIP-nha, identified in the ascomycete Nectria haematococca, and as such, FIP-nha would be the first FIP to be identified outside the order of Basidiomycota. The second is LZ-9, an LZ-8 like protein identified in Ganoderma lucidum. Recombinant FIP proteins were produced in Pichia pastoris and purified using His-affinity magnetic beads. The bioactive characteristics of FIP-nha and LZ-9 were compared to two other well-known FIP proteins, LZ-8 from G. lucidum and FIP-fve from Flammulina velutipes, which were produced and purified using the same method. The produced recombinant FIPs (rFIPs): rLZ-8, rLZ-9, rFIP-fve and rFIP-nha were investigated for their hemagglutinating activity which revealed that rLZ-8, rLZ-9 and rFIP-nha were able to agglutinate rabbit, mouse and sheep red blood cells while rFIP-fve only agglutinated rabbit red blood cells. None of the rFIPs were able to agglutinate human red blood cells unless the cells were trypsinized. In addition, all rFIPs were studied and compared to several lectins for their effect on Caco-2 intestinal cell layer integrity using transepithelial electrical resistance (TEER) measurement. rLZ-9 appeared to have the highest effect in lowering TEER, similar to one of the tested lectins. Testing of rFIPs for their activation of inflammation-related genes of THP-1 macrophages showed rFIP-fve to be the strongest inducer of pro-inflammatory cytokine transcription. These results indicate that each rFIP has a unique bioactive profile as well as each lectin, creating the basis for further studies to relate structure to biological activity.
    Bacterial cell surface deformation under external loading
    Chen, Y. ; Norde, W. ; Mei, H.C. van der; Busscher, H.J. - \ 2012
    mBio 3 (2012)6. - ISSN 2150-7511 - 8 p.
    atomic-force microscopy - staphylococcus-aureus - mechanical-properties - adhesion - biofilms - model - viscoelasticity - peptidoglycan - contact - removal
    Viscoelastic deformation of the contact volume between adhering bacteria and substratum surfaces plays a role in their adhesion and detachment. Currently, there are no deformation models that account for the heterogeneous structure and composition of bacteria, consisting of a relatively soft outer layer and a more rigid, hard core enveloped by a cross-linked peptidoglycan layer. The aim of this paper is to present a new, simple model to derive the reduced Young’s modulus of the contact volume between adhering bacteria and substratum surfaces based on the relationship between deformation and applied external loading force, measured using atomic force microscopy. The model assumes that contact is established through a cylinder with constant volume and does not require assumptions on the properties and dimensions of the contact cylinder. The reduced Young’s moduli obtained (8 to 47 kPa) and dimensions of the contact cylinders could be interpreted on the basis of the cell surface features and cell wall characteristics, i.e., surfaces that are more rigid (because of either less fibrillation, less extracellular polymeric substance production, or a higher degree of cross-linking of the peptidoglycan layer) had shorter contact cylinders and higher reduced Young’s moduli. Application of an existing Hertz model to our experimental data yielded reduced Young’s moduli that were up to 100 times higher for all strains investigated, likely because the Hertz model pertains to a major extent to the more rigid peptidoglycan layer and not only to the soft outer bacterial cell surface, involved in the bond between a bacterium and a substratum surface.
    Liquid droplet-like behaviour of whole casein aggregates adsorbed on graphite studied by nanoindentation with AFM
    Helstad, K. ; Rayner, M. ; Vliet, T. van; Paulsson, M. ; Dejmek, P. - \ 2007
    Food Hydrocolloids 21 (2007)5-6. - ISSN 0268-005X - p. 726 - 738.
    colloidal calcium-phosphate - membrane emulsification - surface evolver - micelles - milk - stability - size - dissociation - microscopy - particles
    AFM measurements in the force volume mode were performed over the total penetration depth for different positions on casein aggregates adsorbed to a graphite surface in a liquid cell. The stiffness of the force curves was correlated to indentation depths, layer depth and lateral position within the aggregates with the aim of arriving at a credible explanation for the shapes of the force curves. The commonly used Hertz-based models did not fit the experimental data. The ratio between the height and diameter of the adsorbed casein aggregates was found to be linear, suggesting surface energy dominated liquid droplet behaviour. To investigate the possibility, numerical simulations were performed using the Surface Evolver, an interactive finite element program for the study of surfaces shaped by surface tension and other energies. Simulated force curves were in good agreement with experimental findings, both with respect to slope as a function of indentation as well as describing the variation with indentation position on the aggregate due to interfacial and geometric effects. By comparing the simulated force curves to the measurement data it was found that there would have been an interfacial energy equivalent to 10 mJ/m2.
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