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Terahertz Subwavelength Fiber
No full text在電磁波頻譜中，兆赫波所位在的頻段是一個非常重要的區域，這個頻段所包含的頻率範圍大約從100GHz - 10THz，是介於微波與光波之間的過渡地帶。由於許多重要的物理現象都發生在這個頻段，兆赫波的相關研究近年來日益受到重視，各種產生及偵測兆赫波的方法也相繼被提出。然而由於大部份的物質對於兆赫波都有很強的吸收，在過去的兆赫波研究中大多都使用自由空間中的金屬反射鏡來改變兆赫波的傳播方向。利用這種方法所建構出來的系統很容易受到外界的干擾且在架設上十分沒有彈性，因此若是缺少一種可靠且低損耗的傳導方法，兆赫波系統在未來的實際應用上勢必會遭遇到很大的困難。有鑒於此，我們提出了一種次波長兆赫波光纖，可以有效地傳導兆赫波並且具有極低的衰減係數(~0.01cm-1)。
我們所設計的兆赫波光纖採用線徑比波長還小的聚乙烯細線或圓管作為核心(core)，並以空氣作為外殼(cladding)。由於線徑小於波長，這種光纖所能傳播的模態只有HE11，且大部份光場都會在空氣中傳播，可以大幅減低兆赫波在傳播過程中被核心介質吸收的程度。此外由於聚乙烯在兆赫波頻段的吸收常數較其他材質為小，因此被限制在核心的光場在傳播過程中也會損失較少的能量。採用上述的架構，我們成功地減少兆赫波在傳輸中的損耗。相信這樣子的兆赫波光纖能夠有效地縮減兆赫波系統的大小並降低系統複雜度，對未來的兆赫波生物影像及分子偵測等等應用的實現有很大的幫助。In the electromagnetic spectrum, terahertz frequencies, which usually defined as those in the range of 100 GHz – 10 THz, form a significant region that connects the microwave and optical-wave bands. Since various important physical phenomena happened in this region, more and more attention had been paid to the investigations of terahertz science in recent years. Many different techniques regarding the generation and detection of terahertz wave were also proposed one after another. However, for the reason that most of the materials have a great absorption constant in the terahertz frequency, the propagation of terahertz wave is usually controlled by metallic reflectors in almost all the applications, which makes the terahertz systems not only vulnerable to environmental disturbance but also inflexible in the construction of application setups. Hence, there will be a lot of difficulties in the future applications of terahertz system for lack of a reliable and low-loss guiding method. In view of this, we proposed and demonstrated a terahertz subwavelength fiber with a very low attenuation constant (~0.01 cm-1) for guiding terahertz wave.
In our design, the sub-wavelength fiber core is made of polyethylene wires or tubes that surrounded by the air serving as the cladding. Due to the sub-wavelength characteristic of the fiber core, the only sustained mode is HE11 which delivers most of the fields in the air cladding, which enormously reduces the degree of core absorption in the propagation. In addition, as polyethylene has a lower absorption constant in the terahertz region, the power delivered in the core will be attenuated less than the cores made of other materials. By adopting above structure, we successfully reduce the loss in terahertz wave guiding which can make the terahertz systems compact and less complex. We believe that it will be very helpful to the realization of terahertz applications such as fiber sensing, biomedical-imaging, and so on.Chapter 1 Introduction 1
1.1 The Basics of Terahertz Technology 1
1.2 An Overview of the Thesis 5
Chapter 2 Construction of a Coherent Tunable Narrow-band 10
Terahertz Source
2.1 Excitation Source - Optical Coherent Control System 10
2.1.1 Grating Pair 11
2.1.2 Michelson Interferometer 13
2.1.3 Discussion 15
2.1.4 Autocorrelation Measurements 17
2.2 Terahertz Photonic Transmitter 28
2.2.1 The Layout of Terahertz Photonic Transmitter 38
2.2.2 Generation of Narrow-band Terahertz Wave 30
Chapter 3 Low-reflectivity Fabry-Perot Interferometer Based 35
Terahertz Fourier Transform Spectrometer
3.1 Theory of the Terahertz Fourier Transform Spectrometer 36
3.1.1 Fabry-Perot Interferometer 36
3.1.2 Fabry-Perot Based Fourier Transform Spectroscopy 39
3.2 Measurement of Terahertz Wave Spectrum 47
3.2.1 Construction of Terahertz Fourier Transform 47
Spectrometer
3.2.2 Spectrum Determination of the Terahertz Source 49
Chapter 4 Characteristic of Subwavelength Terahertz Fiber 55
4.1 The Basic Model of Subwavelength Terahertz Fibers 56
4.1.1 Wave Equation in Plastic Wires 56
4.1.2 Analysis of Low-loss Plastic Wires in Single-mode 59
Condition
4.2 The Subwavelength Terahertz Fiber Measurement 66
4.2.1 Experimental Setup and Fiber Preparation 66
4.2.2 Measurement of Fiber Attenuation 68
4.2.3 Coupling Efficiency of the Subwavelength Terahertz 69
Fiber
4.2.4 Hollow-core Terahertz Fiber 74
Chapter 5 Conclusions 78
5.1 Summary 78
5.2 Future Works 7
The molecular events underlying the compression-induced rapid cortical neuronal dendritic remodeling: an investigation in a rat epidural cerebral compression model
No full text臨床醫學上，大腦在許多的病理情況如: 腦瘤、腦血腫、頭部外傷、水腦症等會有受到擠壓及壓迫的情形，但先前鮮少有研究針對此做探討。鑒於此，我們採用”大鼠硬腦膜外壓迫”的動物模式來探討物理性壓迫對於大腦神經元塑性的影響。我們在大鼠硬腦膜外，植入半圓形輕量硬物，壓迫大鼠體感覺運動區域上方。我們發現，物理性壓迫會立即造成壓迫源下方，大腦皮質內錐狀細胞的樹突發生擠壓及扭曲。在形態上此扭曲變形的樹突，會在持續壓迫3天後回復到原先平直的狀態。受壓迫的錐狀細胞在重新塑形的過程中，伴隨有微管相關蛋白(microtubule-associated proteins)磷酸化的增加。微管相關蛋白磷酸化的增加會使得細胞骨架產生不穩定的狀況，進而使細胞增加塑性以重組細胞形態。我們發現在壓迫後，微管相關蛋白MAP2和tau的磷酸化，分別在壓迫30分鐘到1小時以及壓迫10分鐘到12小時都有增加的情況發生。利用免疫染色方法，亦證實了磷酸化增加的MAP2和tau在受壓迫的錐狀細胞細胞體和樹突內表現量都上升。伴隨著微管相關蛋白磷酸化的增加，我們同時發現在壓迫10分鐘到壓迫1天，去磷酸酶-PP2A的酵素活性會降低，但是去磷酸酶-PP2B的酵素活性則沒有太大改變。在蛋白激酶方面，物理性壓迫會使得蛋白激酶-Erk1/2和p38的活性短暫增加。蛋白激酶和去磷酸酶的活性變化的時程，都和受到壓迫的細胞，形態重新塑形的時程相吻合。本實驗指出，物理性壓迫會立即引起細胞內蛋白激酶和去磷酸酶的活性平衡發生改變，進而導致微管相關蛋白磷酸化程度上升，使得受壓迫的細胞樹突內細胞骨架不穩定，導致壓迫後細胞形態上的改變。綜合上述，大腦受到壓迫時，很快的神經細胞即開始變化，進而造成神經細胞形態乃至於功能上的改變，因此臨床上因病變或外傷而引起腦壓迫時，宜儘速進行解壓迫，以避免細胞型態改變的分子在迅速的被啟動後，造成無法回復的變化
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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