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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Non-chemical alternatives for weed control in containerized plants
No full textWeeds are a serious problem in nursery for container production, because air, nutrient and water are limited by the container volume. Chemical weeding is the main method to control weeds in nurseries but problems as proper calibration, herbicide run-off, need for multiple applications and product cost must be taken into account. The aim of this work was to investigate the degradation time and cost of some environmental-friendly materials used to control weeds in three widely used container-grown shrubs (Photinia ×fraseri 'Red Robin', Prunus laurocerasus 'Rotundifolia', Thuja plicata 'Atrovirens'). 120 plants per species were potted into 3 L containers. Four non-chemical mulching materials were used: 1) coconut fibre discs; 2) vegetal and synthetic fibre discs; 3) viscose fibre discs; 4) a mineral grain mixture without chemical additives (Gerval ®). The effectiveness of these materials was compared with a chemical control (oxadiazon) and with a hand weeding control. Weeds in container were counted and removed every 45 days during two growing seasons (2006 and 2007). Plant height and biomass were recorded at the beginning and at the end of the trial. Vegetal/synthetic fibre discs allowed a weed control as good as the chemical in all the species tested. Due to its short duration this material was replaced at the beginning of the second growing season. Coconut discs and Gerval ® assured a satisfying weed control. No differences between these treatments and vegetal/synthetic fibre discs were found. These materials were applied at the beginning of the experiment and were not replaced in the second year. Serious damages to the root flare were caused by Gerval ®. The viscose fibre discs did not allow a satisfying weed control, because of their quick degradation, and they had to be replaced during the trial. No significant differences in plant height and biomass production were found among treatments. Total cost of weed control (including installation) in the two years of the trial was 0.19 €/pot for coconut discs and 0.20 €/pot for vegetal/synthetic fibre discs. Chemical control allowed weed control with half of the cost, but this value does not take into account chemical externalities and a possible rise of resistances in weeds. Costs of Gerval ®, viscose fibre discs and manual weed removal did not give a result acceptable for nursery production
Effects of Root Severance by Excavation on Growth, Physiology and Uprooting Resistance of Two Urban Tree Species
No full textThis experiment was carried out to evaluate the early physiological and growth response of two shade trees to root damage. European limes (Tilia × europea) and horse chestnuts (Aesculus hippocastanum) were planted in March 2004 and allowed to establish undisturbed for 5 years. In 2009, roots were damaged by either excavating one (MD) or two (SD) trenches at 40 cm from the root flare. Roots were excavated with an AirspadeTM to evaluate root loss caused by trenching. Shoot and diameter growth, leaf gas exchange, chlorophyll fluorescence and leaf water relations were determined up to 26 months after root severance. Results indicate that the growth reduction normally occurring after construction damage is due to reduced leaf gas exchange and less favorable water relations. Also, signs of photoinhibition were found in SD plants, particularly in horse chestnut. Therefore, root loss through trenching induced a mild water stress to severed trees, even in years characterized by high rainfall and water availability. More observations are needed to determine whether trees will be able to recover from damage or will decline further, especially if dryer years will occur before complete root regeneration
Mulching as alternative to chemical weed control in nursery containerized crops
No full textWeed control effectiveness of five mulching materials was determined in three container-grown ornamental crops (Photinia xfraseri 'Red Robin',Prunus laurocerasus 'Rotundifolia' and Thujaplicata 'Atrovirens'). Mulches tested were: AW-Disk® (a by-product of coconut); Basotop® (made of almond drupe shells without glue); two other materials made of vegetal and synthetic fibers; an experimental textile made of both polyester and synthetic absorbent fibers. Two chemicals-Gallery® T-DG (trifluralin + isoxaben) and Ronstar® (oxadia-zon)-were also evaluated in comparison to hand weeding. Weeds were counted and removed from pots twice during the growing season. Where differences in weed number were observed among treatments, mulches tended to provide more effectiveness than chemical products. Moreover, moisture loss was reduced in mulched containers. Mulches did not affect plant growth (dry biomass and height increase during growing season)
Evaluation of zero-runoff irrigation systems for containerized nursery production
No full textWater is a primary resource and its availability for ornamental industry will soon be reduced because of increasing costs and because of competition with other sectors. In addition, in nursery production a noteworthy amount of fertilizers is leached off in the environment with water, causing pollution of the superficial water bodies. Technologies able to rationalize both the irrigation and the fertilization, like closed-loop or capillary mat systems, are a possible solution to reduce both water use and fertilizer leaching. The aim of this study was to test different irrigation systems for nursery ornamental crops, analyzing also the problems linked to reuse of drained solutions. A traditional irrigation system (OI - overhead irrigation) was compared with two zero-runoff systems: A closed system (WR - overhead irrigation with recycling of runoff) and a sub-irrigation system with capillary mat (CM). For each system a 300 m 2 tunnel covered with an anti-hail net was used. About water consumption, CM allowed 26% water savings, while the WR system allowed the saving of 20% of the water. No differences in plant quality were observed among irrigation systems. In the zero-runoff systems economic and ecological benefits are clear. In particular, the system equipped with capillary mat showed the best performances
Effects of shading on growth, leaf gas exchange and chlorophyll fluorescence of three container-grown shrubs
No full textThe aim of this work was to find the optimal level of irradiance for growth and leaf gas exchange in three container-grown widely-used ornamental shrubs (Rhododendron hybr. 'Orion', Choisya ternata H.B.K. and Viburnum ×pragense Vik). One-hundred and twenty rooted cuttings per each species were grown in shadehouses which provided different light environments (full sun, 30% shade and 60% shade). Light intensity was reduced by using commercially available shade material consisting of black woven polypropylene fabric that acted as a neutral filter to PAR. Standard commercial nursery production for fertilization, irrigation and pest control was followed. Plant height, dry weight, and shoot o root ratio were measured at the end of the growing season in 2005 and 2006. Leaf gas exchange and chlorophyll fluorescence were measured in 2006. For Viburnum ×pragense the total leaf number per plant, mean area per leaf, Leaf Area Index (LAI) and Relative Growth Rate (RGR) were measured in 2005 and 2006. Rhododendron hybr. responded to shading by decreasing its transpiration and stomatal conductance. Shaded plants also had lower shoot and root dry weight. Shading increased carbon assimilation of Choisya ternata; plants of this species were also taller and had higher total plant shoot and root dry weights. Viburnum ×pragense showed a great adaptability to the different light environments. Plants grown in full sun and under 60% shade had similar plant dry weight and leaf gas exchange. Our results confirm that response to shade is species-specific. Rhododendron performed better in full sun. Choisya performed better under 60% shade, which may lead to water saving in nursery production of the species, without compromising plant quality. Viburnum can grow both in full sun and 60% shade. In this species, the most shaded plants also showed a higher number of leaves/plant, average leaf area, LAI and LAR especially in the second year
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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