1,721,010 research outputs found
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
Variations on the Author
Get PDF“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
Recommended from our members
Fueling the Brain: Diet’s Impact on the Blood-Brain Barrier and Circadian Biology
No full textThe aim of this dissertation is to investigate how dietary macronutrient composition, particularly ketogenic feeding, influences systemic metabolism, circadian rhythms, physical endurance, and blood-brain barrier function. While the ketogenic diet is employed increasingly for its neuroprotective and metabolic effects, its impact on behavioral rhythmicity and blood-brain barrier physiology remains incompletely understood. This dissertation addresses these knowledge gaps through a multi-modal approach, combining behavioral assays, circadian analyses, and molecular profiling of the blood-brain barrier. In Chapter 2, I characterize how ketogenic feeding alters diurnal and circadian rhythms in mice, revealing a marked sex-dependent effect. Male mice fed a ketogenic diet exhibit significantly earlier onset of activity during the dark cycle, as well as a shortened endogenous circadian period under constant darkness conditions, suggesting a shift in central clock timing. In both sexes, ketogenic diet-fed mice show diminished voluntary locomotion, indicating impairments in physical stamina. Interestingly, female mice exhibit reduced locomotion without corresponding shifts in circadian or diurnal rhythmicity, highlighting a sexually dimorphic behavioral output of metabolic state. In Chapter 3, I examine how different diets affects blood-brain barrier structure, function, and transcriptional identity. While high-fat/high-sucrose and ketogenic diet-fed mice show radically different metabolic phenotypes, neither diet induces overt changes in vesicular transport or tight junction morphology, nor grossly alters permeability to small hydrophilic solutes. However, transcriptomic profiling of isolated brain endothelial cells reveals robust ketogenic diet-induced changes in circadian gene expression, including core clock genes and circadian transcription factors, suggesting circadian modulation at the blood-brain barrier. I then show that the function of the efflux transporter P-glycoprotein displays circadian oscillation in conventionally fed animals, but loses amplitude under ketogenic diet feeding, despite an overall increase in efflux transport levels. These findings show that metabolic state can reprogram the temporal dynamics and magnitude of efflux transport across the blood-brain barrier. Together, these findings reveal that the ketogenic diet exerts profound effects on circadian timing, locomotion, and neurovascular function. By integrating behavioral chronobiology with cellular analyses of the blood-brain barrier, this work reveals how a systemic shift in metabolic fuel utilization can influence both physiological rhythms and neurovascular transport dynamics in the brain
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
Recommended from our members
The Origin and Function of CNS Fibrosis
Get PDFFibrosis is a common pathological response to inflammation in many peripheral tissues and can prevent tissue regeneration and repair. Despite the potential importance, very little is known about the fibrotic response in the central nervous system (CNS), and how this may impact the regenerative process. We identified persistent fibrotic scarring in the brain and spinal cord following neuroinflammation. Using lineage tracing and single-cell sequencing in the EAE mouse model of multiple sclerosis, we determined that this fibrotic scar is derived from proliferative CNS resident fibroblasts, not pericytes or infiltrating bone marrow-derived cells. Ablating proliferating fibroblasts using the fibroblast-specific expression of herpes thymidine kinase led to an increase in oligodendrocyte lineage cells within inflammatory lesions and a reduction in motor disability. We further identified that interferon gamma pathway genes are enriched in CNS fibroblasts, and the fibroblast-specific deletion of Ifngr1 resulted in a reduced fibrotic scar in EAE. Additionally, we identified that platelet derived growth factor receptor signaling affects brain fibroblast development and fibroblast migration. In the retina, fibrosis occurs following retinopathies and can lead to retinal detachment and blindness, and yet little is known about the origin of this fibrosis as it has been difficult to model in mice. We generated a novel mouse model of oxygen-induced retinopathies that exhibits persistent fibrotic pathology, and used histology and single-cell sequencing to determine that the origin of the fibrotic scar in the retina is likely pericytes. These data delineate a framework for understanding CNS fibrosis
Recommended from our members
Brain vasculature in health and disease
Get PDFThroughout the body, the vasculature functions as a delivery system, supplying oxygen and nutrients crucial for cell activity and survival. Central nervous system (CNS) vasculature plays a second critical role as a barrier system, limiting brain entry of bloodborne ions, molecules, and cells. Indeed, CNS blood vessels are endowed with a series of unique properties that allow them to tightly regulate the extracellular environment of the brain, and together these properties are termed the “blood-brain barrier” (BBB). The barrier properties of CNS vasculature are critical for proper brain function; BBB dysfunction during disease or injury can lead to a cascade of consequences resulting in neuronal death. Several questions remain regarding how BBB properties are maintained in health and the mechanisms underlying their dysfunction in neuropathologies. The brain uses an extraordinary amount of the body’s energy, and without constant blood supply from the vasculature, its functions quickly deteriorate. Indeed, neuronal activity leads to a temporary increase in local blood flow to provide neurons with sufficient energy and oxygen, and this phenomenon is known as neurovascular coupling (NVC). NVC has been shown to involve various cell types and signaling molecules, but it is still unclear to what extent endothelial cells, the cells that form the innermost walls of the vasculature, participate in NVC. This dissertation explores brain vasculature in health and disease. Chapter I focuses on BBB dysfunction in disease, identifying PDLIM1 as a marker for BBB dysfunction and characterizing its role in CNS endothelial cells. Chapter II focuses on the neurovascular unit, specifically whether microglia play a role in maintaining barrier properties in healthy vasculature. Chapter III demonstrates the dynamic nature of neurovascular cholesterol metabolism and how this metabolic pathway influences NVC
Recommended from our members
Regulation of the Blood-Brain Barrier by Neural Activity
Get PDFThe blood vessels in the central nervous system (CNS) have a series of unique properties, termed the blood-brain barrier (BBB), which stringently regulate the entry of molecules into the brain, thus maintaining proper brain homeostasis. Despite the dynamic nature of the brain, the BBB has largely been studied in a static context. We sought to understand if the BBB exhibited plasticity and whether neural activity could regulate BBB properties. Using both chemogenetics and a volitional behavior paradigm, we identified a core set of brain endothelial genes whose expression is regulated by neural activity. In particular, neuronal activity regulates BBB efflux transporter expression and function, which is critical for excluding many small lipophilic molecules from the brain parenchyma. Furthermore, we found that neural activity regulates the expression of circadian clock genes within brain endothelial cells, which in turn mediate the activity-dependent control of BBB efflux transport. These results have important clinical implications for efficiency of CNS drug delivery in the day vs. night, the BBB’s role in clearance of CNS waste products including Aβ in health and Alzheimer’s Disease, and understanding how neural activity can control these and other diurnal processes
Combining gamma neuromodulation and robotic rehabilitation after a stroke restores parvalbumin interneuron dynamics and improves motor recovery in mice
Get PDFStroke is a leading cause of long-term disability, frequently associated with persistent motor deficits. Gamma band oscillations, generated by synchronous discharge of parvalbumin-positive interneurons (PV-INs), are critically affected after stroke in humans and animals. Both gamma band and PV-INs play a key role in motor function, thus representing a promising target for poststroke neurorehabilitation. Noninvasive neuromodulatory approaches are considered a safe intervention and can be used for this purpose. Here, we present a novel, clinically relevant, noninvasive, and well-tolerated sub-acute treatment combining robotic rehabilitation with advanced neuromodulation techniques, validated in a mouse model of ischemic injury. During the sub-acute poststroke phase, we scored profound deficits in motor-related gamma band activity in the perilesional cortex. These deficits were accompanied by reduced PV-IN firing rates and increased functional connectivity, both at the perilesional and at the whole-cortex levels. Therefore, we tested the therapeutic potential of coupling robotic rehabilitation with optogenetic PV-IN-driven gamma band stimulation in a subacute poststroke phase during motor training to reinforce the efficacy of the treatment. Frequency-specific movement-related gamma band stimulation, when combined with physical training, significantly improved forelimb motor function. More importantly, by pairing robotic rehabilitation with a clinical-like noninvasive 40 Hz transcranial Alternating Current Stimulation, we achieved similar motor improvements mediated by the effective restoring of movement-related gamma band power, improvement of PV-IN maladaptive network dynamics, and increased PV-IN connections in premotor cortex. Our research introduces a new understanding of the role of parvalbumin-interneurons in poststroke impairment and recovery. These results highlight the synergistic potential of combining perilesional gamma band stimulation with robotic rehabilitation as a promising and realistic therapeutic approach for stroke patients.TN
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
