1,721,011 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
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
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
Inhibition of hepatitis B virus replication by shRNAs: A new strategy in HBV treatment
No full textRNA interference (RNAi) can be defined as sequence- spesific mRNA degradation. RNAi mechanism is initiated by small interfering RNA (siRNA) and results in silencing of an active gene transcript. siRNAs are spesific for only target mRNAs. So no mRNA other than target one can be degraded with RNAi mechanism. Our purpose in this study is to investigate effects of shRNAs targeting three different sites of hepatitis B virus mRNAs on the viral replication in HepG2.2.15cells. MATERIAL- METHOD: Three HBV-specific siRNAs were designed targeting X (1686- 1705), Core (2228- 2247) and S (765-784 nt.) transcripts. These siRNAs were cloned to PENTRY/U6 vector for expression of shRNAs (small hairpin RNAs). HepG2.2.15, a stable HBV producing cell line, was used to see the effects of shRNAs on HBV. The cells were transfected with shRNA expressing plasmids (P765, P2228 and P1686 targeting X, core and S region respectively) or a mock plasmid targeting lacZ gene. Transfection efficiency was determined by using green flourescent protein expressing plasmid. After transfection viral DNA levels were detected. RESULTS: The culture media was collected in the days 2, 3, 4, 5, 6, 7 posttransfection and analyzed by Real-time PCR. Viral DNA production suppressed for 7 days. The HBV DNA levels were decreased by 81 %, 76 %, 75 % with P765, P2228 and P1686 vectors respectively. Whereas viral DNA level was increased with mock plasmid (PlacZ). DISCUSSION: In conclusion, the siRNAs designed for X, core and S regions, spesifically and significantly suppressed HBV DNA. Our results support the potential use of this treatment strategy in hepatitis B. Keywords: RNAi, siRNA, shRNA, HBV, HepG2.2.15 cell line. 78RNAi (RNA interference: RNA çatışması) kısaca sekans spesifik mRNA degradasyonu olarak tanımlanabilir. RNAi işlemi siRNA'larla (small interfering RNA: küçük engelleyici RNA molekülleri) başlar ve aktif bir gen transkriptinin (mRNA) susturulması (gene silencing) ile sonuçlanır. Bu moleküller çok spesifik olduklarından hedef mRNA dışında başka mRNA'ları yıkıma uğratmazlar. RNAi teknolojisi sadece virüslere ve diğer hastalıklara karşı potansiyel bir tedavi aracı olarak değil aynı zamanda genlerin fonksiyonunu anlamada da yeni ve güçlü bir araçtır. Bu çalışmanın amacı RNAi mekanizmasını HBV'ye karşı kullanmak yoluyla HBV replikasyonunun in-vitro ortamda baskılanmasıdır. MATERYAL VE YÖNTEM: HBV mRNA sekanslarına spesifik, 21 nükleotid uzunluğunda, X, kor ve yüzey genlerini hedef alan üç siRNA tasarlandı. Bu siRNA'lar shRNA ("small hairpin RNA") ekspresyonu sağlamak için klonlandı. İlk olarak siRNA'ların pENTR/U6 vektörüne ligasyonu yapıldı. Elde edilen bu vektör kompetent E. Coli'ye transforme edildi. Klonlama sekans analizi ile onaylandı. shRNA'ların HBV üzerindeki etkisini görmek için stabil HBV ekspresyonu ve replikasyonunun yapıldığı insan hepatoma hücre hattı HepG.2.2.15 kullanıldı. Transfeksiyon katyonik lipozomlarla gerçekleştirildi. Transfekte edilen shRNA'ların HBV replikasyon düzeyine etkisi kantitatif "real-time PCR" yöntemi ile değerlendirildi. BULGULAR: Viral DNA düzeyine 2., 3., 4., 5., 6. ve 7. günlerde bakıldı. Bunun sonucunda viral DNA replikasyonunun 6 gün boyunca baskılandığı görüldü. HBV DNA düzeyi, yüzey bölgesini hedef alan plazmidle 81%, kor bölgesini hedef alan plazmidle 76% ve X bölgesini hedef alan plazmidle 75 % baskılandı. SONUÇ: Bu çalışma ile HBV replikasyonun shRNA'lar kullanılarak baskılanabildiği gösterilmiştir. Bu baskılama RNAi'nin HBV'ye karşı potansiyel bir tedavi aracı olarak kullanılabileceğini düşündürmektedir. Anahtar sözcükler: RNAi, siRNA, shRNA, HBV, HepG2.2.15 hücre hattı. 7
Kronik Lenfositik Lösemide TCTP/HRF ve Mcl-1'in ifadelenmesi
No full textKronik Lenfositik Lösemi (KLL) erişkinde en sık görülen lösemi tipidir. Genetik yatkınlık dışında etyolojik bir faktör saptanamamıştır. KLL'de apoptoz mekanizmasının bozulduğu, apoptozu önleyen Bcl-2, Mcl-1 gibi proteinlerin yüksek düzeyde ifade edildiği bilinmektedir. Bu antiapoptotik proteinlerin aşırı ifadesinin tedavi yanıtı ve sağkalımı olumsuz etkilediği saptanmıştır. Translasyonel Kontrol Edilen Tümör Proteini (TCTP) şu ana dek çalışılan tüm ökoryatlarda görülen, evrimsel olarak iyi korunmuş çok işlevli bir proteindir. İşlevleri arasında hücre proliferasyonunu indüklemesi, apoptozu engellemesi, histamin salınımını uyarması, immün yanıtta hücreler arası sinyal molekülü rolü ve B hücre proliferasyonunu uyarması sayılabilir. TCTP şaperon bir proteindir. Antiapoptotik Mcl-1'e bağlanır ve onu kararlı hale getirir. TCTP bazı kanser tiplerinde aşırı ifade edilir ve ifadesinin azaltılması kanser hücrelerinin yaşamasını olumsuz etkiler. U937 ve diğer tümör hücrelerinde siRNA ve antisens oligonükleotidler kullanılarak TCTP ifadesi inhibe edildiğinde apoptozun arttığı görülmüştür. Tuynder ve ark.nın yaptığı bir diğer çalışma malign hücrede TCTP'nin baskılanmasının tümör geri dönüşümü / iyileşmesine (?tumor reversion?) neden olduğunu göstermiştir (Tuynder M. ve ark., 2002 ve 2004). Literatürde KLL TCTP ilişkisini inceleyen bir çalışma yoktur. TCTP ve Mcl-1 KLL patogenezinde, hastalığın ilerlemesi ve tedavi direncinde rol oynayabilir. KLL lenfositlerinde TCTP seviyesi protein (akım sitometri, western blot) ve mRNA (Gerçek zamanlı polimeraz zincir reaksiyonu: ?Real time PCR?) düzeyinde belirlendi ve hasta olmayan normal insanlarınkiyle karşılaştırıldı. Yapılan çalışmada TCTP ve Mcl-1 KLL hastalarında sağlıklı bireylere göre anlamlı düzeyde yüksek saptanmıştır (p< 0,001). TCTP ve Mcl-1 düzeyleri arasında çok kuvvetli ilişkili gözlenmiştir (p< 0,001). Ancak KLL'de TCTP ve Mcl-1 düzeyleri ile hastalığın evresi, sitogenetik anormallikler ve CD38 düzeyi arasında ilişki bulunmamıştır. AbstractChronic Lymphocytic Leukemia (CLL) is one of the most common types of leukemia in adults. There is no etiological factor except for familial predisposition. Apoptotis mechanism in CLL is defective and CLL cells overexpress several antiapoptotic proteins including bcl-2 and Mcl-1. Overexpression of antiapototic proteins have a negative impact on chemotherapy response and survival in CLL patients. Translationally Controlled Tumor Protein (TCTP) is a highly conserved, multi-functional protein that is expressed in all studied eukaryotic organisms up to now. TCTP has several functions including induction of cell proliferation, histamine release, inhibition of apoptosis and a role of signal molecule between cells in immune system. TCTP is a shaperon protein which binds Mcl-1 and stabilizes it. TCTP is overexpressed in several cancer types. Inhibition of expression of TCTP using siRNA and antisense oligonucleotides in U937 and other tumor cells, increase apoptosis, negatively effects the survival of cancer cells and induces tumor reversion (Tuynder M. et.al. 2002 and 2004). There is no study searching CLL and TCTP relationship in the literature. Antiapoptotic and stimulatory functions of TCTP and Mcl-1 for B cell proliferation may have a role in CLL patogenesis, disease pregression and chemotherapy resistance. TCTP were determined as protein (flow cytometry and western blotting) and mRNA (Real-time PCR) levels in CLL lymphocytes and compared with those of normal healthy individuals. TCTP and Mcl-1 levels were significantly higher in CLL patients with respect to the healty people in this study (p< 0,001). TCTP and Mcl-1 levels were significantly correlated with each other (p< 0,001). However, TCTP and Mcl-1 levels in CLL were not significantly correlated with the stage of the disease, cytogenetic abnormalities and CD38
Adli Bilimler ve Kriminalistik Ansiklopedisi, Adli Mühendislik ve Adli Bilişim-2 (Cilt 10)
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