117,322 research outputs found
Alien Registration- Vigue, Edward L. (Bath, Sagadahoc County)
No full texthttps://digitalmaine.com/alien_docs/8755/thumbnail.jp
Sperm maturity and the extent of DNA degradation in sperm fractions prepared by various methods
No full textAlien Registration- Vigue, Rudolph L. (Dexter, Penobscot County)
No full texthttps://digitalmaine.com/alien_docs/11039/thumbnail.jp
Morphometric assessment of mature and diminished-maturity human spermatozoa: sperm regions that reflect differences in maturity,
No full textAneuploidy frequencies in mature and immature spermatozoa classified by the absence or presence of cytoplasmic retention: an assessment with fluorescence in situ hybridization
No full textPreviously, a relationship has been found between diminished cellular maturity of human spermatozoa and low-level expression of the testis-specific chaperone protein, HspA2. Because HspA2 is a component of the synaptonemal complex in rodents, and assuming that this is also the case in men, it was postulated that the frequency of chromosomal aneuploidies would be higher in immature versus mature spermatozoa. This question was examined in spermatozoa from semen and from 80% Percoll pellets (enriched for mature spermatozoa) of the same ejaculate in 10 oligozoospermic men. Immature spermatozoa with retained cytoplasm, which signifies spermiogenetic arrest, were identified by immunocytochemistry. Using fluorescence in-situ hybridization (FISH), ∼7000 sperm nuclei were evaluated in each of the 20 fractions (142 086 spermatozoa in all) using centromeric probes for the X, Y and 17 chromosomes. The proportions of immature spermatozoa were 45.4 ± 3.4 versus 26.6 ± 2.2% in the two semen versus the Percoll groups (medians: 48.2 versus 25%, P < 0.001, n = 300 spermatozoa per fraction, total 6000 spermatozoa). There was also a concomitant decline in total disomy, total diploidy and total aneuploidy frequencies in the 80% Percoll versus semen fractions (0.17 versus 0.54%, 0.14 versus 0.26% and 0.31 versus 0.81% respectively, P < 0.001 in all comparisons). The mean decline of aneuploidies was 2.7-fold. With regard to the hypothesis that aneuploidies are related to sperm immaturity, there was a close correlation between the incidence of immature spermatozoa and disomies (r = 0.7, P < 0.001) but no correlation with diploidies (r = 0.03), indicating that disomies originate primarily in immature spermatozoa. It is suggested that the common factor underlying sperm immaturity and aneuploidies is the diminished expression of HspA2. In addition, the lack of this chaperone may also cause diminished cellular transport of proteins, such as DNA-repair enzymes or of the retention of cytoplasm that is extruded from normally maturing spermatozoa during spermiogenesis
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
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