1,721,099 research outputs found
Plumatella marlieri Wiebach 1970
No full textPlumatella marlieri Wiebach, 1970 (Fig. 6 a–c) Plumatella marlieri Wiebach, 1970: p. 73, figs 12–18. Material examined. No. 441, labeled as a holotype, collected August, 1959 from DR. Congo at the Aquarium at Ndakalas, Uvira, Lake Tanganyika, by G. Marlier. Description. The brief diagnosis by Wiebach (1970) is confirmed in this excellent specimen. Zooids occur in clusters attached loosely to leaves of Vallisneria and joined to other clusters by linear series of two or more zooids. The colony wall is completely transparent and mostly colorless, becoming light brown in older tubules (Fig. 6a). There are no apparent septa, no raphe, and no incrustation. Floatoblast valves are similarly transparent, colorless, and somewhat fragile (Fig. 6b). When valves are separated the annulus becomes almost invisible compared to the light yellow coloring of the capsule. Small, well-spaced tubercles on the fenestra appear as dark spots under the compound microscope (Fig. 6c). Floatoblast dimensions are shown in Table 2. The specimen has no sessoblasts. Distribution. The species is known from a single collection at the northern tip of Lake Tanganyika. Remarks. In this species Wiebach described both thin-walled leptoblasts and “pycnoblasts” which was his term for the more typical robust form of floatoblast. However, my own search found only one form which was lightly sclerotized. Some of these were hatching inside the colony, which is uncommon but not unusual among plumatellids, especially in tropical waters. While it is possible that some of these statoblasts forego the standard period of dormancy, there was no sign of new zooids developing inside the intact statoblasts, as occurs in leptoblasts of P. casmiana. There were also no newly established colonies on the substratum, suggesting that floatoblasts were not hatching immediately after their release. The specimen was collected by Georges Marlier, then Director of the Central African Institute for Scientific Research in Uvira. In a letter to Wiebach he wrote, “The collection was taken from a large tank for rearing fish…fed continuously by water pumped from Lake Tanganyika across from our laboratory. Therefore, the growth environment was artificial, although the water came in a direct line from the lake.” (Wiebach 1970).Published as part of Wood, Timothy S., 2020, Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species, pp. 581-600 in Zootaxa 4820 (3) on page 589, DOI: 10.11646/zootaxa.4820.3.11, http://zenodo.org/record/439798
Hyalinella africana Wiebach 1964
No full textHyalinella africana Wiebach, 1964 (Fig. 2 a–c) Hyalinella africana Wiebach, 1964: p. 32 –34, text figs 24–26, pl. 11 (40–41). Plumatella evelinae: Lacourt, 1968: 81–83, pl. 11(e). Material examined. Specimen Nos. 204 and 205 from Lukoma, Rwanda (both labeled “ Typus ”), No. 267 from Lake Mugesera, Rwanda, 33 km SE Kigali; and No. 439 from Lake Tanganyika. All specimens are well preserved with polypides extended (Fig. 2a, b). No. 205 is probably in the best condition, consisting of three fairly large colonies. Description. In his original description, Wiebach (1964) accurately described the spindle-shaped colonies growing around plant stems. The zooid body wall is clear, colorless, and soft (Fig. 2a, b). Notable is what Wiebach described as the “common colonial ectocyst (forming) a hard-gelatinous mass, which is filled with fine detritus and epizoic unicellular organisms and over which the orifice of the individuals rises at intervals like a hump or fingertip.” In fact, in some of the preserved material the entire colonial mass has started to peel away intact from the plant stem. Wiebach described and illustrated (with photos) two types of floatoblasts: pycnoblasts and leptoblasts (Wiebach 1964, figs. 23, 24). Unfortunately, among all three specimens I was able to find only a single floatoblast, in Specimen No. 267, not yet fully developed, corresponding roughly to Wiebach’s “pycnoblast” (Fig. 2c). The two valves are about equally convex. The overall length = 311 μm, width = 195 μm; the dorsal fenestra length = 181 μm, width = 144 μm; ventral fenestra length = 19 μm, width = 162 μm. Distribution. Known only from Rwanda and south to Lake Tanganyia. Remarks. Wiebach worked under the assumption that many plumatellid species had two types of floatoblasts: robust pycnoblasts and more delicate leptoblasts. In the case of H. africana any such distinction is slight and can be attributed to normal variation. With the single remaining floatoblast, I separated the valves for detailed examination (Fig. 2c) and isolated them in a small vial, now included in the larger vial with Specimen No. 267. Although Wiebach described (but did not illustrate) sessoblasts in this species none could be found among any of the MRAC specimens. Assuming his written diagnosis is correct, the presence of sessoblasts would preclude accommodating this species in the genus Hyalinella. According to the current understanding, no sessoblasts are produced in this genus (Wood et al. 2006). The thick gelatinous base suggests a possible affinity with Gelatinella toanensis (Hozawa & Toriumi, 1940), but the validity of that genus remains questionable. At this time, I am reluctant to move the species to the already unwieldy genus Plumatella. Recognizing these difficulties, the species name, Hyalinella africana, should remain unchanged until more specimens become available.Published as part of Wood, Timothy S., 2020, Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species, pp. 581-600 in Zootaxa 4820 (3) on page 585, DOI: 10.11646/zootaxa.4820.3.11, http://zenodo.org/record/439798
Plumatella ruandensis Wiebach 1964
No full textPlumatella ruandensis Wiebach, 1964 (Fig. 9 a–c) Plumatella ruandensis Wiebach, 1964: p. 15, pl. 4 (13–15). Plumatella casmiana Lacourt, 1968: p. 54. Material examined. No. 206, type specimen, collected 6 June 1952 in Rwanda at Lake Burera, 60 km NNW Kigali, Northern Province, Burera District, by Hubert Damas. Description. Colonies have grown completely around narrow stems like a sheath. The soft ectocyst is colorless and transparent (Fig. 9a). While the colonies are tubular many tubules are firmly adhered to each other. Floatoblasts are less than 400 μm in length (Table 2), lightly tuberculated, and show a clear size difference between dorsal and ventral fenestrae (Fig. 9b). Scanning electron microscopy reveals that cells of the annulus are individually highly convex (Fig. 9c). Sessoblasts have a wide annulus that is faintly reticulated; the frontal valve bears fine tubercles. Distribution. The species is known only from its type locality in Rwanda. Remarks. The specimen is in excellent condition, including abundant floatoblasts and sessoblasts.Published as part of Wood, Timothy S., 2020, Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species, pp. 581-600 in Zootaxa 4820 (3) on pages 593-594, DOI: 10.11646/zootaxa.4820.3.11, http://zenodo.org/record/439798
Customer Reactions in Out-of-Stock Situations – Do promotion-induced phantom positions alleviate the similarity substitution hypothesis?
Full text linkOut-of-Stock (OOS) is a prevalent problem customers face at the POS. In this paper, we demonstrate both theoretically and empirically how OOS-induced substitution patterns can be explained and predicted by means of context and phantom theory. We further analyze the relevance of promotions, for which OOS is most pronounced, as essential driver of differences in customers’ OOS reactions. The results of an online experiment demonstrate that customers substitute unavailable items in accordance to a negative similarity effect which is reduced, however, for OOS items on promotion. The empirical findings further suggest that customers’ OOS responses differ for promoted vs. non-promoted items. We find that customers being affected by a stock-out of promotional products significantly more often postpone purchases and tend to avoid substitution resulting in severe losses for the retailer. However, for non-promoted items, customers easily switch to alternative brands. That way, manufacturers lose profit and possibly loyal customers.Out-of-Stock, Context Effects, Phantoms, Promotion, Consumer Decision Making
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
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
Context Effects as Customer Reaction on Delisting of Brands
Full text linkThe delisting of brands is frequently used by retailers to strengthen their negotiating position with the manufacturers and suppliers of their product assortment. However, retailers and manufacturers have to consider the risk of potential reactions when customers are faced with a reduced or modified assortment and thus, different choice. In this paper, two studies are presented which investigate customers` switching behavior if a (sub-)brand is unavailable and key determinants of the resulting behavior are discussed. Various conditions are tested by taking into account context theory. The results reveal that customer responses depend significantly on the context. A real-life quasi-experiment suggests that manufacturers may encounter substantially larger losses than retailers. Managerial implications for both parties can be derived and recommendations for further research are developed.Consumer decisions, delisting, context effects, switching behavior, retailing, logistic regression
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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