1,721,004 research outputs found
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
Quantitative analysis of intracranial compliance using MRI
Full text link【目的】非侵襲的に頭蓋内環境を評価するために,磁気共鳴画像(MRI)を使用して頭蓋内コンプライアンスを測定した.
【方法】頭蓋内コンプライアンス指標(ICCI : intracranial compliance index)は,phase-contrast(PC) cine MRIで測定した心周期における正味の頭蓋流入出血液および脳脊髄液流量から求めた最大頭蓋内容積変化と最大圧力勾配変化の比から得た.ファントム実験および正常圧水頭症例および脳萎縮または無症候性脳室拡大例,健常ボランティアにおいて,ICCIを比較検討した.同時に,髄液時間流量波形伝達関数の積分値から求めた頭蓋内力学的特性を表す時定数を測定した.さらに,ICCIの血流動態依存性を確認するために,acetazolamide静脈注入前後における変化も解析した.以上の値は,シャント手術時において測定した侵襲的コンプライアンス測定であるpressure volume response(VPR)と比較した.
【結果】正常圧水頭症群におけるICCIは,脳萎縮または無症候性脳室拡大群および健常ボランティア群よりも有意に小さかった.しかし,無症候性脳室拡大群と健常ボランティア群においては,有意な違いは認められなかった.また,acetazolamide注入前後で,ICCIの有意な変化は認められなかった(血流動態と独立).ICCIと時定数との比較においては,よく一致していた.ICCIとVPRは強い負の相関が認められた.
【結論】PC cine MRIで測定したICCIによるコンプライアンス解析は,非侵襲的に詳細な頭蓋内環境の状態を評価可能であり,正常圧水頭症の補助的診断となりうる.To assess a state and dynamics of the intracranial system noninvasively, intracranial compliance was measured with magnetic resonance imaging (MRI).
The intracranial compliance (ICC) index was obtained from the ratio of the maximum intracranial volume loading change to the maximum pressure gradient change during the cardiac cycle, which were calculated from the net transcranial blood and cerebrospinal fluid (CSF) flow measured with phase-contrast (PC) cine MRI. ICC indices were determined in patients with normal pressure hydrocephalus (NPH), brain atrophy or asymptomatic ventricular dilation (VD), and in healthy volunteers. Concurrently, a time constant of the integral of the CSF wave response function, which represents the intracranial mechanical property was determined with PC cine MRI. The changes in ICE indices were also analyzed after intravenous injection of acetazolamide, i.e., hemodynamics independent. These values were then compared with the volume-pressure response (VPR) as a invasive compliance measurement during the shunt operations.
The ICC index in the NPH group was significantly lower than in the control or VD group, but no difference was found between the control and VD groups. There was no significant change in the ICC index after acetazolamide injection. There were significant correlations between the ICC index and the time constant. A negative correlation was noted between the ICC index and the VPR.
Compliance analysis with ICC index measured by PC cine MRI makes it possible to obtain noninvasively a more detailed intracranial state and dynamics in the NPH and to assist in diagnosis of the NPH.研究課題/領域番号:15591261, 研究期間(年度):2003-2005出典：「MRIによる頭蓋内コンプライアンスの定量解析」研究成果報告書 課題番号15591261
(KAKEN：科学研究費助成事業データベース（国立情報学研究所）)
本文データは著者版報告書より作成research repor
Hemodynamically independent analysis of intracranial cerebrospinal fluid dynamics using PC cine MRI
Full text link正常圧水頭症(NPH)における頭蓋内の力学的特性を明らかにするために,phase contrast(PC)cine MRIを使用してdriving vascular pulsationと中脳水道における脳脊髄液(CSF)流量波形から算出した周波数位相伝達関数(PTF)を評価した.
中脳水道長軸上の中点の垂直面において,CSF流量波形と血流量波形を心電同期PC cine MRIを使用して測定した.各心時相における脳へ流入する動脈と脳から流出する静脈の差分を入力関数(driving vascular pulsation), CSF流量波形を出力関数として,力学的特性に関与するPTFを両関数から算出した.くも膜下出血後のNPH症例(SAH-NPH)およびSAH-NPHのシャント手術後例,健康正常ボランティアについてPTFを測定した.また,acetazolamide経静脈注入(脳血液量上昇)5分後においてもPTFを測定した.さらに頭蓋内コンプライアンスの指標であるpressure volume response(PVR)とPTFを比較した.
SAH-NPH群の基本波におけるPTFは,健康正常ボランティア群よりも有意に大きかった.また,SAH-NPHシャント手術後群のPTFは,健康正常ボランティア群と同一傾向を呈した.acetazolamide注入後のPTFは,注入前と比較して全周波数において有意な差が認められなかった.これはPTFが血流動態に依存しないことを示している.基本波におけるPTFとPVRは正の相関が認められた.
PC cine MRIを使用してPTFを解析することで,NPH症例における頭蓋内の力学的特性が非侵襲的に得られる.To clarify intracranial dynamical properties in normal pressure hydrocephalus (NPH), we assessed a spectral phase transfer function (PTF) calculated from the driving vascular pulsation and cerebrospinal fluid (CSF) flow in the aqueduct using phase contrast (PC) cine MRI.
On a vertical plane against a mid-point on the long axis of the aqueduct, both CSF flow and blood flow waveforms were measured with cardiac triggered PC cine MRI. Taking the difference in each cardiac phase between arterial inflow and venous outflow in the brain as the input function (driving vascular pulsation), and the CSF flow in the aqueduct as the output function, the PTF related to the dynamical properties was calculated from both functions. The PTF was determined in patients with NPH after a subarachnoid hemorrhage (SAH-NPH), in an SAH-NPH post-shunt operation group, and in healthy volunteers (control group). The PTF(f)s were also measured 5 min after an intravenous injection of acetazolamide (increase of cerebral blood volume). The PTF was compared with the pressure volume response (PVR) as an index of the intracranial compliance.
The PTF of the 1st harmonic in the SAH-NPH group was significantly larger than in the control group, and the PTF in the SAH-NPH post-shunt operation group tends to be closer to that in the control group than the SAH-NPH group. There was no significant difference in PTF before and after acetazolamide injection at any frequency ; independent of hemodynamics. A positive correlation was noted between the PTF
PTF analysis with PC cine MRI makes it possible to obtain information noninvasively on intracranial dynamical properties in cases of NPH.研究課題/領域番号:13670923, 研究期間(年度):2001-2002出典：「PC cine MRIによる血流動態に依存しない頭蓋内脳脊髄液循環動態解析」研究成果報告書 課題番号13670923
(KAKEN：科学研究費助成事業データベース（国立情報学研究所）)
本文データは著者版報告書より作成research repor
Analysis of regional brain elasticity using MRI
Full text link磁気共鳴画像から脳局所の弾性を評価する方法を確立し, 非侵襲的に頭蓋内環境の局所変化を伴う病変の診断に役立てることを試みた. 心周期における脳局所の水分子拡散の変化量および頭蓋内容積変化との関係を検討した結果, 心周期における水分子拡散の変化量は, 脳の局所弾性に関与し, 正常圧水頭症の診断に役立つと結論付けた.研究課題/領域番号:18591331, 研究期間(年度):2006-2008出典：「MRIによる脳の局所弾性解析」研究成果報告書 課題番18591331
（KAKEN：科学研究費助成事業データベース（国立情報学研究所））
（https://kaken.nii.ac.jp/report/KAKENHI-PROJECT-18591331/18591331seika/)を加工して作成research repor
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
