1,241,361 research outputs found
The Nascent Polypeptide-Associated Complex Modulates
No full textsed on our results, we define two distinct modes of interaction between SRP and the ribosome--nascent chain complex: salt-resistant interactions between SRP54 and signal sequences, and salt-sensitive interactions between additional components of SRP and the ribosome. We conclude that NAC does not directly influence signal sequence recognition by SRP but, rather, that it negatively modulates interactions that occur between SRP and the ribosome itself. These results are discussed in terms of a model wherein SRP and NAC regulate each others' activity during protein targeting. Background In eucaryotic and procaryotic cells, signal sequences that direct proteins into the secretory pathway contain few structural features that distinguish them from other proteins. In general, clusters of as few as seven consecutive hydrophobic amino acids function as signal sequences. In yeast, about 20 % of random peptide sequences can function as signal sequences (although many function with lo
Solute dispersion under electric and pressure driven flows; pore scale processes
No full textSolute dispersion is one of the major mixing mechanisms in transport through porous media, originating from velocity variations at different scales, starting from the pore scale. Different driving forces, such as pressure driven flow (PDF) and electro-osmotic flow (EOF), establish different velocity profiles within individual pores, resulting in different spreading of solutes at this scale. While the velocity profile in PDF is parabolic due to the wall friction effects, the velocity in EOF is typically plug flow, due to the wall charge effects. In this study, we applied a pore network modeling formulation to simulate the velocity field driven by pressure and electric potential to calculate and compare the corresponding average solute dispersivity values. The influence of different driving forces on the hydrodynamic dispersion of a tracer solute is investigated. Applying the pore network modeling, we could capture the velocity variations among different pores, which is the main contribution for the dispersion coefficient. The correlation between pore velocities against pore sizes is found to be different for EOF and PDF, causing different solute dispersion coefficients. The results can provide insight into modeling of electrokinetic remediation for contaminant cleanup in low permeable soils
Electrostatic Interactions Between Glycosaminoglycan Molecules
No full textThe electrostatic interactions between nearest-neighbouring chondroitin sulfate glycosaminoglycan (CS-GAG) molecular chains are obtained on the bottle brush conformation of proteoglycan aggrecan based on an asymptotic solution of the Poisson-Boltzmann equation the CS-GAGs satisfy under the physiological conditions of articular cartilage. The present results show that the interactions are associated intimately with the minimum separation distance and mutual angle between the molecular chains themselves. Further analysis indicates that the electrostatic interactions are not only expressed to be purely exponential in separation distance and decrease with the increasing mutual angle but also dependent sensitively on the saline concentration in the electrolyte solution within the tissue, which is in agreement with the existed relevant conclusions
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
The interactions between biodiversity and climate change and the actions required to tackle both issues simultaneously and synergistically
Get PDFThis briefing paper considers the relationship between the biodiversity and climate crises, the interactions between them, and why an integrated approach is essential to creating a sustainable future where people and planet can thrive
Plant basal resistance: genetics, biochemistry, and impacts on plant-biotic interactions
No full textBasal resistance depends largely on a diverse range of defence mechanisms that become active upon attack by pathogens or insects. These mechanisms range from rapid stomatal closure and production of reactive oxygen species, to callose deposition and defence gene induction. It is commonly assumed that the speed and intensity of these inducible defences determines the effectiveness of basal resistance. The present dissertation describes different aspects of basal resistance in Arabidopsis thaliana and Zea mays. Chapter 2 of the dissertation describes natural variation between Arabidopsis accessions in basal defence responsiveness to pathogen-associated molecular patterns (PAMPs) and the defence hormone salicylic acid (SA). Quantitative trait loci (QTL) analysis identified different loci regulating the sensitivity of PAMP-induced callose and SA-induced defence gene expression. One QTL controlling SA responsiveness was found to contribute to basal resistance against Pseudomonas syringae pv. tomato. In Chapter 3, the contribution of benzoxazinoids (BXs) in basal resistance of maize is described, using maize bx1 mutant lines that are impaired in the first dedicated step of BX biosynthesis. Compared to wild-type lines, bx1 lines displayed reduced penetration resistance against aphids and fungus. Furthermore, infestation of wild-type plants by aphids and fungi stimulated the conversion of DIMBOA-glucoside into HDMBOA-glucoside and DIMBOA, which was most pronounced in the apoplast of challenged tissues. Interestingly, these events preceded major tissue damage or symptom development, suggesting that BX-dependent basal resistance does not necessarily depend on tissue damage. Upon further investigation of wild-type and bx1 mutant lines, we observed significantly reduced callose deposition in bx1 plants after PAMP treatment. Furthermore, DIMBOA infiltration of the apoplast mimicked PAMP-induced callose in wild-type plants. Hence, DIMBOA acts as a regulatory signal in the expression of cell wall-based basal resistance of maize. BXs have also been reported to act as allelopathic signals belowground, which are further investigated in Chapter 4. Chromatographic analysis revealed that DIMBOA is the dominant BX species in root exudates of maize. To investigate the impact of BXs on root-colonizing rhizobacteria, transcriptome analysis was performed of DIMBOA-treated Pseudomonas putida KT2440. This global analysis pointed towards increased transcription of bacterial genes that are involved in break-down of aromatic metabolites and chemotaxis. The latter response was confirmed by in vitro assays, which demonstrated chemotaxis of the bacteria towards DIMBOA. Furthermore, root colonisation assays with GFP-expressing P. putida KT2440 revealed that wild-type plants allowed more bacterial colonization than BX-deficient bx1 plants, indicating that BXs can recruit rhizobacteria from the soil. Preliminary results that are presented in Chapter 5 show that root colonization by P. putida KT2440 primes aboveground basal defences against herbivores, thereby further highlighting the central and multifaceted function of DIMBOA in maize basal resistance
Spreading in functional phonology
No full textThe occurrence of and the restrictions on the temporal spreading of phonological feature values (assimilation, harmony) are the results of interactions between the functional principles of minimizing articulatory effort and minimizing perceptual confusion. This proposal is tested on the typology of opacity to nasal spreading. While the sonority approach of Gnanadesikan (1995) meets with insuperable problems with regard to the position of /h/ in the hierarchy, and the feature-geometric representational approach of Piggott (1992) needs to take recourse to ad-hoc conditions in UG in order to get the hierarchy right, the functional approach accurately predicts the attested typology.The definitive version of this article was published in Functional Phonology: Formalizing the Interactions Between Articulatory and Perceptual Drives (1998) and is available at http://www.fon.hum.uva.nl/paul/Boersma, P. (1997). Spreading. In Functional phonology: Formalizing the interactions between articulatory and perceptual drives (pp. 441-460). The Hague: Holland Academic Graphics.ISBN: 9789055690541 (Published book
Sound change in Functional Phonology
No full textSound systems may never stop changing, not even if only internal factors are present, because there may always be a better system. Non-teleological random variation of constraint ranking defines a pressure that explains the existence of perpetually rotating cycles of sound changes.The definitive version of this article was published in Functional Phonology: Formalizing the Interactions Between Articulatory and Perceptual Drives (1998) and is available at http://www.fon.hum.uva.nl/paul/Boersma, P. (1997). Sound change. In Functional phonology: Formalizing the interactions between articulatory and perceptual drives (pp. 381-414). The Hague: Holland Academic Graphics.ISBN: 9789055690541 (Published book
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
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