1,720,986 research outputs found
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
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
Effects of warming procedures on the survivability of in vitro matured buffalo (Bubalus bubalis) oocytes vitrified by Cryotop.
No full textThe aim of this work was to evaluate the effects of different warming procedures on the survivability of buffalo in vitro matured oocytes vitrified by the Cryotop (CT) method. In vitro matured oocytes were vitrified in a final solution of 20 % ethylene glycol (EG), 20 % of dimethyl sulfoxide (DMSO) and 0.5 M sucrose. In Group A oocytes (n = 111) were warmed in 1.25 M sucrose for 1 min and then exposed to decreasing concentrations of the sugar (0.625, 0.42 and 0.32 M for 30 sec). In Group B, oocytes (n = 122) were warmed into a 0.25 M sucrose solution for 1 min, and then exposed to a 0.15 M sucrose solution for 5 min. Oocytes were rinsed and allocated into the in vitro maturation (IVM) drops for 2 h and then fertilized in vitro. The survival rate was significantly higher in Group A compared to Group B both at 2 h post-warming (92.8 vs 83.6 %; P<0.05) and at 20 h post-warming (85.6 vs 50 %; P<0.01). Cleavage rate was also significantly increased in Group A compared to Group B (55.3 vs 36.3 %; P<0.01) whereas no differences were observed in the blastocyst yield between groups (7.8 % vs 6.9 %)
Effect of osteopontin on in vitro embryo development in cattle.
No full textOsteopontin (OPN) is an acidic single-chain phosphorylated glycoprotein found both in the oviduct fluid (ODF) and oviductal epithelium in cattle, which is believed to facilitate fertilization. It was recently reported that addition of a rabbit polyclonal immunoglobulin G antibody against purified bovine milk OPN with sperm oocytes, bovine oocytes, or both decreased (P < 0.05) fertilization compared with the in vitro-fertilized control (Goncalves et al. 2007 Theriogenology 67, 468–74). The aim of the present work was to determine the effect of in vitro addition of OPN to the fertilization medium on both cleavage and postfertilization embryo development in cattle. In the first experiment, in vitro-matured oocytes were fertilized in modified TALP medium in the presence of 0.0, 0.1, 1.0, or 10 μg mL–1 of OPN. In a second experiment, matured oocytes were in vitro-fertilized in modified TALP medium in the presence of 0.0, 10, 20, or 40 μg mL–1 of OPN. In vitro fertilization was carried out with frozen–thawed spermatozoa from a bull previously tested for IVF. After 20 to 22 h of coincubation at 39°C, 5% in CO2 in air, presumptive zygotes were vortexed to remove cumulus cells, washed, and transferred, 30 to 50 per well, into 400 μL of SOF modified medium. Zygotes were incubated in a humidified mixture of 5% CO2, 7% O2, and 88% N2 in air at a temperature of 39°C. On Day 7 of development (Day 0 = day of insemination), cleavage and development rates into transferable embryos (TE)–tight morulae (TM) and blastocysts (Bl) of superior quality were recorded. Differences in the percentages of both cleavage and blastocyst rates among groups were analyzed by a chi-square test. In experiment 1, numerically higher percentages of TM–Bl (29.5, 29.5, 30.5, and 37.5%, respectively, in the control group and in the groups with 0.1, 1, and 10 μg mL–1 of OPN; P = 0.25) and Bl (28.6, 27.5, 29.1, and 36.7, respectively, in the control group and in the groups with 0.1, 1, and 10 μg mL–1 of OPN; P = 0.24) were observed with 10 μg mL–1 of OPN. In experiment 2, significantly more cleavage (80.0 v. 71.3%; P < 0.05) and higher percentages of TM–Bl (44.6 v. 34.5%; P < 0.05) and Bl (39.2 v. 30.6%; P = 0.06) were observed with 10 μg mL–1 of OPN v. the control. Combined analysis from both experiments showed an overall effect of 10 μg mL–1 of OPN v. the control in the percentages of TM–Bl and Bl (respectively, 41.1 v. 33.3% and 37.7 v. 30.5%; P < 0.05)
Open pulled straw vitrification for in vitro produced buffalo (Bubalus bubalis) embryos.
No full textThe aim of this study was to compare the efficiency of different combinations of cryoprotectants for vitrification of IVP buffalo (Bubalus bubalis) embryos at different developmental stages by the open pulled straw (OPS) method. In method A, we evaluated the vitrification and warming solutions previously used to vitrify buffalo embryos in French straws (Gasparrini et al. 2001 Theriogenology 55, 307). Embryos were equilibrated in 1.4 M glycerol for 5 min before being placed into 1.4 M glycerol + 3.6 M ethylene glycol (EG) for 5 min. Then, embryos were transferred into 3.4 M glycerol + 4.6 M EG for 25 s and loaded into the OPSs. For warming, OPSs were briefly immersed in a 0.5 M sucrose solution; the embryos were exposed to 0.25 M sucrose for 5 min before transfer to SOF medium for culture. In Method B, we examined the vitrification and warming solutions previously used for OPS vitrification of cattle embryos (Vajta et al. 1998 Mol. Reprod. Dev. 51, 53-58). Buffalo embryos were equilibrated in 7.5% EG + 7.5% dimethyl sulfoxide (DMSO) for 3 min before transfer into 16.5% EG + 16.5% DMSO and 0.5 M sucrose. After 25 s, they were loaded into the OPSs. For warming, embryos were recovered in a 0.25 M sucrose solution and transferred into a 0.15 M sucrose solution for 5 min before being placed in SOF medium. A total of 293 IVP buffalo embryos (eight replicates) were vitrified at Day 7 of culture (Day 0 = in vitro fertilization). Embryos were vitrified at the following developmental stages: early blastocyst (eBL, n = 26 and 34 with methods A and B, respectively), blastocyst (Bl, n = 31 and 35 for Methods A and B, respectively), expanded blastocyst (XBl, n = 29 and 38 for Methods A and B, respectively), and hatched blastocyst (HBl, n = 46 and 54 for Methods A and B, respectively). Embryo survival rate was determined as the percentage of vitrified-warmed embryos undergoing further development during a 24-h in vitro culture period. Differences between methods were analyzed by ANOVA following arcsine transformation of data. The overall embryo survival rate recorded at 24 h was not significantly different between Methods A and B (70% vs. 62%, respectively). Specifically, no differences were observed in embryos vitrified at the eBL (70% vs. 73%, A and B, respectively), Bl (69% vs. 70%, A and B, respectively), and HBl (46% vs. 36%, A and B, respectively) stages. In contrast, a significantly higher survival rate was recorded for XBl-stage embryos vitrified-warmed by Method A as compared to Method B (90% vs. 53%, respectively; P < 0.01). In Method A, survival rate of XBl was significantly higher than that of HBl (P < 0.05), but it was not different from that of eBl and Bl. Within Method B, the survival efficiency was similar for eBL, BL, and XBl, whereas survival rate of HBl was significantly lower (P < 0.05). In conclusion, although overall embryo survival in vitro was similar between methods, the combination of cryoprotectants used in Method A seemed more suitable for vitrification of IVP buffalo embryos at the XBl stage
Effect of co-culture during fertilization of buffalo (Bubalus bubalis) in vitro-matured denuded oocytes vitrified by Cryotop.
No full textAlthough removal of cumulus cells improves the efficiency of vitrification of buffalo (Bubalus bubalus) in vitro-matured (IVM) oocytes (Gasparrini et al. 2007 Anim. Reprod. Sci. 98, 335–342), the lack of cells impairs the fertilization process. Therefore, the aim of the present work was to evaluate the influence of a somatic support during in vitro fertilization (IVF) of buffalo vitrified denuded matured oocytes. Since IVF on a cumulus cells monolayer was inefficient, we verified the effects of co-culture with cumulus-enclosed oocytes (COCs). IVM buffalo oocytes (n = 316) were vitrified by the Cryotop® method (Kuwayama and Kato 2000, J. Assist. Reprod. Genet. 17, 477 abst) that was recently proven suitable for buffalo oocyte cryopreservation (Attanasio et al. 2006 Reprod. Domest. Anim. 41, 302–310). Denuded buffalo oocytes were equilibrated in 10% ethylene glycol (EG) and 10% dimethyl sulfoxide (DMSO) for 3 min, transferred into 20% EG and 20% of DMSO in TCM199 with 20% fetal calf serum (FCS) + 0.5 m sucrose, loaded on Cryotops, and plunged into liquid nitrogen within 25 s. For warming, oocytes were exposed for 1 min to 1.2 m sucrose and then to decreasing concentrations of the sugar (0.6, 0.4, 0.3 m for 30 s) in TCM199 + 20% FCS. Oocytes were rinsed and allocated to IVM drops for 1.5 h. Survival rate was evaluated at this point and the oocytes that had survived (292/316 = 92.4%) were split into 2 fertilization groups: (A) approximately 5 buffalo oocytes per 50-μL drop of IVF medium, and (B) approximately 3 buffalo oocytes + 3 bovine fresh COCs per 50-μL drop of IVF medium. Since buffalo COCs easily lose their cells following IVF, for better identification we used bovine COCs that have a brighter and more compact cumulus mass. In vitro fertilization and culture were carried out as previously described (Gasparrini et al. 2007). As control, buffalo oocytes (n = 104) were in vitro-matured, fertilized, and cultured up to the blastocyst stage. On Day 1, survival rate was evaluated in the two vitrification groups; cleavage and blastocyst rates were recorded on Days 5 and 7, respectively, in all groups. The experiment was repeated 4 times. Differences in the percentages of survival, cleavage, and blastocyst formation among treatments were analyzed by chi-square test. Within vitrification groups, despite similar survival rates on Day 1 (90.6% v. 93.3%, respectively, in Groups A and B), cleavage rate was significantly improved in Group B compared to Group A (59.2% v. 45.4%, respectively; P < 0.01). Interestingly, the cleavage rate in Group B was not significantly different from that recorded in the control group (71.0%). Although blastocysts were produced in both vitrification groups (3.6% v. 4.1%, respectively, in Groups A and B), the yield was significantly lower than that of the control group (29.0%, P < 0.01). In conclusion, co-culture with bovine COC during fertilization improves the capability of buffalo denuded vitrified oocytes to cleave
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