124,937 research outputs found
Detrimental effects of polyvinylpyrrolidone on the ultrastructure of spermatozoa (Notulae seminologicae 13)
No full textThe effect of in-vitro treatment by polyvinylpyrrolidone (PVP) on the ultrastructure of human spermatozoa has been tested previously with the statistical analysis of B. Baccetti et al. PVP had a primary detrimental action on the plasma membrane, as well as on acrosomal and mitochondrial membranes. Furthermore, membrane damage induces deterioration of the chromatin, axonemal tubules, fibrous sheath, and accessory fibres
The spermatozoon of Arthropoda. VI. Ephemeroptera
No full textIn this work the spermatozoon of Chloëon dipteron (Ephemeroptera) is examined. The three most important features are that (a) the acrosome is very brief; (b) the mitochondrial derivative is represented by a long mitochondrion with transverse cristae and by a crystalline mass enveloped in a separated membrane; (c) the axial filament of the tail lacks the two principal central units and the central sheath, and is therefore, of the 9 + 9 +0 pattern. This type of flagellum has not previously been described. © 1969 Academic Press, Inc
Zoogeographical expeditions of the C.N.R. ship "Minerva" around the small circumsardinian islands: a synthesis.
No full textGoing 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
Intelligenza artificiale e gruppi di società
No full textIl contributo esamina il possibile ruolo positivo dell'intelligenza artificiale quale strumento di gestione e controllo a servizio della direzione e coordinamento. Viene poi approfondita la possibilità di costituire in diritto italiano società controllate a guida autonoma (self-driving subsidiaries) così come prospettate nella letteratura giuridica straniera. I vincoli di diritto societario italiano inducono ad approfondire anche l'ipotesi della configurabilità di un patrimonio destinato a gestione algoritmica. All'esito di tali considerazioni si pone in evidenza come la gestione algoritmica di persone giuridiche o patrimoni autonomi al fondo sollevi un problema più ampio relativo all'individuazione dei presupposti organizzativi che sono richiesti dall'ordinamento per l'esercizio di attività imprenditoriale in regime di responsabilità limitata
Scanning electron microscopy and human sperm pathology
No full textThis paper has been carried out in order to inquire whether some of the best known human malformations can be recongnized by scanning electron microscopy. The SEM appearance of 'straight tailed', 'empty tailed', 'short tailed', 'round headed', and related to the inner structure. Straight tails and empty tails are quite evident at SEM. These defects are due to severe axonemal defects, related to dynein and tubulin deficiencies: '9+0', 'arm less' and 'axoneme less' spermatozoa are included in this category. Short tails and round heads are still more evident defects, and round heads are still more evident defects, due to complete absence of tail structures or acrosome and easily recognizable at SEM. Double spermatozoa are consistently in patients having abnormally high prolactin level and SEM is obviously sufficient for the diagnosis. Finally, spermatozoa in aged individuals show in SEM a peculiar shapse due to absence of immature stages, reduced cytoplasm, disordered axoneme. It is concluded that SEM examination is a good tool for the identification of most of the best known human sperm abnormalities
Fractionally spaced versus T-spaced adaptive equalization for high level QAM radio systems
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