1,720,996 research outputs found
Proton Spin-Lattice Relaxation in Silkworm Cocoons: Physisorbed Water and Serine Side-Chain Motions
No full textThe molecular dynamic behavior of silkworm cocoons produced by a single Bombyx mori strain was investigated by means of high- and low-resolution solid-state NMR experiments. Cocoons with different moisture content were prepared to study the effects of physisorbed water on their molecular dynamics in the MHz regime, which was probed through the measurement of 1H T1 relaxation times at 25 MHz in the 25-95 °C temperature range. The water content of the different samples was determined from the analysis of 1H free-induction decays. In addition to the rotation of methyl groups, mostly from alanine, and to the reorientation of physisorbed water molecules, already identified in previous works as relaxation sinks, the reorientation of serine side-chains was here found to contribute to 1H T1 above room temperature. The analysis of the trends of 1H T1 versus temperature was carried out in terms of semiempirical models describing the three main motional processes, and indicated that methyl rotation, water reorientation and serine side-chain motions are the most efficient relaxation mechanisms below 0 °C, between 0 and 60 °C, and above 60 °C, respectively. The activation energies were found to decrease passing from serine to water to methyl motions
The Circadian Clock in Lepidoptera
Full text linkWith approximately 160,000 identified species of butterflies and moths, Lepidoptera are among the most species-rich and diverse insect orders. Lepidopteran insects have fundamental ecosystem functions as pollinators and valuable food sources for countless animals. Furthermore, Lepidoptera have a significant impact on the economy and global food security because many species in their larval stage are harmful pests of staple food crops. Moreover, domesticated species such as the silkworm Bombyx mori produce silk and silk byproducts that are utilized by the luxury textile, biomedical, and cosmetics sectors. Several Lepidoptera have been fundamental as model organisms for basic biological research, from formal genetics to evolutionary studies. Regarding chronobiology, in the 1970s, Truman’s seminal transplantation experiments on different lepidopteran species were the first to show that the circadian clock resides in the brain. With the implementation of molecular genetics, subsequent studies identified key differences in core components of the molecular circadian clock of Lepidoptera compared to the dipteran Drosophila melanogaster, the dominant insect species in chronobiological research. More recently, studies on the butterfly Danaus plexippus have been fundamental in characterizing the interplay between the circadian clock and navigation during the seasonal migration of this species. Moreover, the advent of Next Generation Omic technologies has resulted in the production of many publicly available datasets regarding circadian clocks in pest and beneficial Lepidoptera. This review presents an updated overview of the molecular and anatomical organization of the circadian clock in Lepidoptera. We report different behavioral circadian rhythms currently identified, focusing on the importance of the circadian clock in controlling developmental, mating and migration phenotypes. We then describe the ecological importance of circadian clocks detailing the complex interplay between the feeding behavior of these organisms and plants. Finally, we discuss how the characterization of these features could be useful in both pest control, and in optimizing rearing of beneficial Lepidoptera
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
Solid state NMR investigation of the molecular dynamics of cocoon silks produced by different Bombyx mori (Lepidoptera) strains
No full textCocoons produced by different strains of Bombyx mori larvae were investigated by a combination of several high- and low-resolution 1H and 13C solid-state NMR techniques in order to characterize and compare their dynamic behavior at a molecular level. A detailed interpretation in terms of molecular motions in these very complex systems was possible thanks to the integrated analysis of different relaxation measurements and high-resolution selective experiments. Untreated cocoons of all strains were found to be mainly constituted by two different types of rigid domains and by a third one, more mobile, due to physisorbed water molecules. Dynamic processes in the MHz and kHz ranges were characterized by means of different 1H and 13 relaxation times. Cocoons arising from different strains exhibit a different content of physisorbed water and also slightly different dynamic behavior, especially in the MHz regime
Capacità d'attrazione di cultivar di Morus spp. nei confronti di larve in prima età di bombyx mori L. (Lepidoptera, Bombicidae): l'alimentazione con dieta sostitutiva come metodo d'indagine
No full textPreliminary studies on the cryopreservation of silkworm (Bombyx mori)
Full text linkDeveloping a technique for the cryopreservation of Bombyx mori L. germplasm may provide significant benefits for supplying good strains to farmers and facilitate the conservation of living material in genetic banks. Producing species-specific protocols for the selection of the most apt embryonic stage, dechorionation/permeabilization of eggshells, and the acclimation at low temperature before the treatment of eggs at cryogenic temperature is a prerequisite for cryopreservation of B. mori embryos. In this research, non-diapausing eggs of B. mori Nistari strain were used to study cold hardiness; the final aim was to select the most apt embryonic development stages, and in addition, reliable permeabilization, and vitrification treatments. Polyhybrid B. mori eggs of a diapausing strain were also used for comparison in experiments of embryogenesis, permeability, and acclimation under low temperature before cryopreservation. The Nistari eggs in the stage of 24 hours post-oviposition (h PO) showed a scarce survival rate (0.1%) after their submersion in liquid nitrogen (LN), while the highest survival in loading and dehydration with cryoprotective agents was assessed in 40h PO eggs. Overwintering diapausing eggs preserved for three months at 5 degrees C and then treated with various vitrification solutions gave rise to good hatching rates. The achieved results show that it is possible to improve the method of cryopreservation of B. mori eggs by obtaining a good permeability with cryoprotectants at loading/dehydration steps and by decreasing the toxicity, reducing the treatment time
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