1,721,087 research outputs found
CR1 allelic distribution in healthy italians and SLE patients
No full textComplement receptor type 1 (CR1; CD35), the receptor for C3b/C4b, has a molecular weight polymorphism involving four co-dominantly expressed alleles CR1*1, CR1*2, CR1*3 and CR1*4. The most common allotype in the Caucasian population is CR1*1. Previous studies on the frequency of the CR1 allele in Systemic Lupus Erythematosus (SLE) patients reported conflicting results. Recently an increased frequency of the CR1*2 allele was reported in Caucasian SLE patients. The aim of our study is to assess the frequency of CR1 structural alleles in a sample of the Italian population and in a cohort of Italian SLE patients equally distributed nationwide. We found that the most common phenotype was CR1*1.1 (71%) and the other phenotypes found were CR1*1.2 (25%), CR1*1.4 (3%), and CR1*2.2 (1%). Our data show that the allelic frequency distribution in healthy Italians is not different from that of other Caucasian cohorts reported in previous studies. Moreover, the structural polymorphism frequencies in the Italian population show no difference between SLE patients and healthy individuals
METODI DI STUDIO DELLA VARIABILITA’ DELLA FREQUENZA CARDIACA
No full textLa frequenza cardiaca (FC) è controllata dal sistema nervoso vegetativo. Il nodo senoatriale (SA) ha una frequenza propria di depolarizzazione spontanea conosciuta come “frequenza intrinseca” che rappresenta la frequenza misurata in assenza di impulsi simpatici o parasimpatici come si può
ottenere con la denervazione o il blocco farmacologico. Nei soggetti normali la
frequenza intrinseca è di circa 100 bpm e dipende dal sesso e dall’età ed è
influenzata dall’esercizio fisico, l’ipossia e le variazioni di temperatura. I soggetti
allenati a sport di resistenza hanno una frequenza intrinseca minore. Gli effetti del sistema simpatico e parasimpatico influenzano in maniera predominante la FC intrinseca e determinano la FC attuale in quanto l’attivazione parasimpatica riduce la FC, mentre l’attivazione simpatica aumenta la FC. Inoltre l’effetto di una componente è associato ad un aumento dell’attività della sua controparte, fenomeno che è stato definito come “antagonismo accentuato”. L’analisi tradizionale dell’elettrocardiogramma (ECG), considera soltanto gli intervalli tra i complessi elettrocardiografici QRS (intervalli RR) più o meno lunghi trascurando la differenza negli intervalli RR. La variabilità della frequenza cardiaca (HRV) è rappresentata dalle differenze negli intervalli RR e dalle
conseguenti variazioni istantanee della FC. Essa è un indice fisiologico di queste differenze in risposta a fattori quali la posizione, il movimento, il ritmo del respiro
e gli stati emozionali. In questa review vengono analizzati i metodi di studio, i
limiti di normalità e gli effetti di diverse condizioni fisiologiche sulla HRV
EFFETTI DELL'ALLENAMENTO ALLE ATTIVITÀ SPORTIVE SULLA MASSA VENTRICOLARE SINISTRA
No full textLe attività sportive agonistiche comportano adattamenti cardiaci morfologici e funzionali che permettono di ottimizzare la funzione cardiaca durante l’esercizio fisico. Il principale adattamento funzionale cardiaco è rappresentato dalla bradicardia a riposo, conseguente al raggiungimento di un nuovo equilibrio della bilancia simpato-vagale. Il principale adattamento morfologico dell'apparato cardiocircolatorio all’esercizio fisico è rappresentato dall'ipertrofia miocardica, caratterizzata da un aumento della massa cardiaca che deve essere armonico e proporzionale al grado ed al tipo di attività fisica praticata. Tale ipertrofia coinvolge sia la componente miocitaria che quella vascolare per mantenere un’adeguata vascolarizzazione della massa muscolare cardiaca aumentata. La componente fibrocitaria risulta non aumentare come nelle forme di ipertrofia cardiaca patologica, evitando quindi diminuzioni della distensibilità cardiaca o incrementi dello stress parietale, che rappresentano le conseguenze negative delle forme patologiche irreversibili. Tali adattamenti variano in relazione a fattori ereditari (genotipo), età ed epoca di inizio dell’attività sportiva e tipo ed intensità dei programmi di allenamento, in quanto i modelli di allenamento [resistenza (endurance); potenza (power/strenght); misto (resistenza/potenza)] determinano differenti adattamenti morfologici e funzionali.
I dati riportati in questa review permettono di individuare i parametri di studio degli adattamenti cardiaci strutturali e funzionali e di definire i limiti di normalità. Particolare attenzione deve essere riservata alla valutazione della massa, degli spessori di parete e delle dimensioni interne del ventricolo sinistro. Conoscendo i valori massimi di questi parametri morfologici è possibile differenziare il cuore d’atleta, condizione fisiologica, dalla cardiomiopatia ipertrofica e dalla cardiomiopatia dilatativa, condizioni che predispongono ad aritmie cardiache potenzialmente fatali durante l’esercizio fisico
On the accuracy of the segmentation process and transcatheter heart valve dimensions in TAVI patients
No full textAccurate segmentation of medical images is critical for generating patient-specific models suitable for computational analyses, particularly in the context of transcatheter aortic valve implantation (TAVI). This study aimed to quantify the accuracy of the segmentation process from medical images of TAVI patients to understand the uncertainty in patient-specific geometries. We also quantified discrepancies between actual and CT-related diameter measurements due to artifacts and intra-observer variability. Segmentation accuracy was assessed using both synthetic phantom models and patient-specific data. The impact of voxelization and CT scanner resolution on segmentation accuracy was evaluated, while the intersection over union (IoU) metric was used to compare the consistency of different segmentation methodologies. The voxelization process introduced a marginal error (<1%) in phantom models relative to CAD models. CT scanner resolution impacted segmented model accuracy only after a 7.5-fold increase in voxel size compared to the baseline medical image. IoU analysis revealed higher segmentation accuracy for calcification (93.4 ± 3.1 %) compared to the aortic wall (85.4 ± 8.4 %) and native valve leaflets (75.5 ± 6.3 %). Discrepancies in THV diameter measurements highlighted a ∼5 % error due to metallic artifacts, with variability among observers and at different THV heights. Errors due to voxel size, segmentation methodologies and CT-related artifacts can impact the reliability of patient-specific geometries and ultimately computational predictions used to asses clinical outcomes and enhance decision-making. This study underscores the importance of accurate segmentation and its standardization for patient-specific modeling of TAVI simulations
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
- …
