1,720,976 research outputs found
A Light Scattering Investigation of Enzymatic Gelation in Self-Assembling Peptides
Full text linkSelf-assembling peptides (SAPs) have been increasingly studied as hydrogel–former gelators because they can create biocompatible environments. A common strategy to trigger gelation, is to use a pH variation, but most methods result in a change in pH that is too rapid, leading to gels with hardly reproducible properties. Here, we use the urea–urease reaction to tune gel properties, by a slow and uniform pH increase. We were able to produce very homogeneous and transparent gels at several SAP concentrations, ranging from (Formula presented.) to (Formula presented.). In addition, by exploiting such a pH control strategy, and combining photon correlation imaging with dynamic light scattering measurements, we managed to unravel the mechanism by which gelation occurs in solutions of (Formula presented.) -based SAPs. We found that, in diluted and concentrated solutions, gelation follows different pathways. This leads to gels with different microscopic dynamics and capability of trapping nanoparticles. At high concentrations, a strong gel is formed, made of relatively thick and rigid branches that firmly entrap nanoparticles. By contrast, the gel formed in dilute conditions is weaker, characterized by entanglements and crosslinks of very thin and flexible filaments. The gel is still able to entrap nanoparticles, but their motion is not completely arrested. These different gel morphologies can potentially be exploited for controlled multiple drug release
Short-time self-diffusion in binary colloidal suspensions
Full text linkThe Brownian dynamics of a colloidal particle is consistently modified by the presence in the solvent of other particles of comparable size, whose effects on the particle diffusion coefficient cannot be attributed to a change of the effective solvent viscosity. So far, despite their impact on subjects ranging from microrheology to phoretic transport in crowded environments, a detailed experimental survey of these effects is still lacking. By exploiting the peculiar properties of fluorinated colloidal particle, we have performed an extensive dynamic light scattering (DLS) investigation of short-time self-diffusion in binary colloidal mixtures, focusing on systems where one of the two species (the “tracer” particles) is very diluted compared to the other one (the “host” particles). From the dependence on the host concentration of the DLS correlation function, we have obtained the first-order correction h s 1 s to the tracer single-particle diffusion coefficient, varying the tracer-to-host size ratio q in the range 0.2 ≤ q ≤ 2. Our results support the functional relation of h s 1 s on q proposed to account for the theoretical and numerical results for hard-sphere mixtures. However, h s 1 s seems to have a weaker dependence on the size ratio than theoretically predicted, possibly because of an imperfect matching of the suspensions we used for an ideal hard-sphere mixture. This may be due to the presence of a stabilizing surfactant layer on the particle surface that, although very thin, has significant effects on hydrodynamic lubrication forces
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
The interplay between childhood maltreatment and eating disorder psychopathology: an hybryd model combining network and mediation analyses
No full textAppropriate 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
Adult attachment style and salivary alpha-amylase and emotional responses to a psychosocial stressor in women with eating disorders
No full textBackground: The fine-tuning of the endogenous stress response system, which includes the hypothalamus-pituitary-adrenal axis and the sympathetic nervous system (SNS), is influenced by early attachment relationships. A higher prevalence of insecure attachment has been detected in people with eating disorders (EDs). Thus, we investigated the emotional and the SNS reactivity to the Trier Social Stress Test (TSST) in women with EDs in relation to their attachment profiles. Methods: Fifty women with EDs and 20 healthy women participated into an experimental study. Attachment was evaluated by Experience in Close Relationship questionnaire. Salivary α-amylase (sAA) levels were measured to assess the SNS reactivity to TSST while the emotional response was measured by the STAI state scale. Results: Compared to women with EDs and low attachment anxiety and healthy controls, women with EDs and high attachment anxiety showed lower TSST-induced sAA production without difference in anxiety scores. Women with EDs and high attachment avoidance showed similar sAA response to TSST but higher levels of anxiety scores compared to those with low attachment avoidance and healthy controls. Conclusions: Our findings corroborate the idea that adult attachment may be associated with variability in emotional and biological responses to a psychosocial stressor in women with EDs
Gut microbiome and psychopathology: a prospective study in patients with anorexia nervosa
No full textThe connection between childhood maltreatment and eating disorder psychopathology: a network analysis study in people with bulimia nervosa and with binge eating disorder
No full textPurpose: Childhood maltreatment (CM) experiences are associated with heightened risk of Eating disorders (EDs). The psychopathological pathways promoting this association in people with Bulimia nervosa (BN) and in those with Binge eating disorder (BED) are under-investigated. Methods: One hundred and eighty-one people with BN and 144 with BED filled in the Eating Disorder Inventory-2, to measure ED psychopathology, and the Childhood Trauma Questionnaire, to assess their early traumatic experiences. Network analysis was conducted to investigate the interplay between those variables. The shortest pathways function was employed to investigate the shortest out of all routes conveying the association between CM and ED-specific symptoms. Results: In both people with BN and with BED, all CM types were connected to the ED psychopathology through the emotional abuse node. The association between emotional abuse and ED-specific symptoms (bulimia and body dissatisfaction) differed in the two groups: in people with BN, it included ineffectiveness, while in people with BED, it involved impulsivity. Interoceptive awareness, an indirect measure of emotion regulation, was included in these pathways in both groups. Conclusion: In the light of literature showing that emotional abuse has a connecting role between CM and ED psychopathology also in anorexia nervosa, the present findings support the idea that emotional abuse conveys such association in all the main ED diagnoses. Ineffectiveness and impulsivity may represent the specific psychopathological dimensions connected to emotional abuse and promoting the maintenance of ED-specific symptoms in BN and in BED, respectively. These findings are worth of attention by clinicians. Level of evidence: Level III: evidence obtained from well-designed cohort or case–control analytic studies
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