169 research outputs found
Fluorescence Properties of 6-Aryl-2´-deoxy-furanouridine and –pyrrolocytidine and their derivatives
No full text2'-deoxyfuranouridine derivatives presenting various aryl groups have been synthesized through Cu(I)-catalyzed intramolecular cyclizations. Moreover, corresponding pyrrolo-dC derivatives have been synthesized and both families of compounds thoroughly characterized using UV/vis and fluorescence spectroscopy as well as time-dependent density functional theory calculations. The photophysical characterization, show that our newly synthesized derivatives of the important pyrrolo-dC family have high fluorescence quantum yields (QYs) and brightness values. Pyrrolo-dC derivative, 3a, shows an environment sensitive QY of up to >60% and brightness of almost 3000, in low polarity solvents and excitation and emission maxima between 365-381 nm and 479-510 nm, respectively, in solvents of different polarities. Two other derivatives, 3b and 3c, show high QYs and brightness values of up to 3300 that are fairly insensitive to their microenvironment. These promising photophysical features suggest future applicability as fluorescent nucleobase analogs.11Nsciescopu
Detection of cofilin mRNA by hybridization-sensitive double-stranded fluorescent probes
No full textWe have developed hybridization-sensitive fluorescent oligonucleotide probes that, in the presence of quencher strands, undergo efficient fluorescence quenching through the formation of partial DNA/DNA duplexes. In the presence of target RNA, rapid displacement of the quencher strands results in highly enhanced fluorescence.11sciescopu
Low-rank estimation and embedding learning: theory and applications
No full textIn many real-world applications of data mining, datasets can be represented using matrices, where rows of the matrix correspond to objects (or data instances) and columns to features (or attributes). Often the datasets are in high-dimensional feature space. For example, in the vector space model of text data, the feature dimension is the vocabulary size. If representing a social network using an adjacency matrix, the feature dimension corresponds to the number of objects in the network. Many other datasets also fall into this category, such as genetic datasets, images, and medical datasets. Even though the feature dimension is enormous, a common observation is that the high-dimensional datasets may (approximately) lie in a subspace of smaller dimensionality, due to dependency or correlation among features. This thesis studies the problem of automatically identifying the low-dimensional space that high-dimensional datasets (approximately) lie in based on dimension reduction models: one is low-rank estimation models and the other is embedding learning models. For data matrices, low-rank estimation is to recover an underlying data matrix, subject to the constraint the matrix is of reduced rank. Such analysis is also generalized to the high-dimensional higher-order tensor data. Meanwhile, embedding learning models are to directly project the observation data into a low-dimensional vector space.
In the first part, the theoretical analysis of low-rank estimation models is established in the regime of high-dimensional statistics. For matrices, the low-rank structure corresponds to the sparsity of the singular values; while for tensors, the low-rank model can be defined as the low-rankness of the unfolding matrices of the tensor. To achieve low-rank solutions, two categories of regularization are imposed. Firstly, the problem of robust tensor decomposition with gross corruption is considered. To recover the underlying true tensor and corruption of large magnitude, structure assumptions of low-rankness and sparsity are imposed on the tensor and corruption, respectively. The Schatten-1 norm is applied as convex regularization for the low-rank structure. Secondly, the problem of matrix estimation is considered with a nonconvex penalty. Compared with convex regularization, nonconvex penalty takes advantage of the large singular values, which leads to faster statistical convergence rate and oracle property under a mild condition on the magnitude of the singular values. For both problems, efficient optimization algorithms are proposed, and extensive numerical experiments are conducted to corroborate the efficacy of the proposed algorithms and the theoretical analysis.
In the second part, embedding learning models for real-world applications are presented. The high-dimensional data is projected into a low-dimensional vector space via preserving the proximity among objects. Each object is represented by a low-dimensional vector, called embedding or distributed representation. In the first application, the heterogeneity of the objects is considered. Based on the observation that several interactions among the strongly-typed objects happen simultaneously as an event, the embeddings of objects in each event are learned as a whole. In other words, the model preserves the proximity among all the participating objects in each event. Experimental results provide evidence that the learned embeddings are more effective while being robust to data sparsity and noises for various classification tasks. In the second application, the task of expert finding is studied, which is to rank candidates with appropriate expertise based on a given query. To capture the subtle semantic information regarding specific queries with narrow semantic meanings, locally-trained embedding learning with concept hierarchy as guidance is proposed for query expansion. The locally-trained embeddings preserve the proximity among terms constrained on a sub-corpus. Compared with global embedding trained on the whole dataset, locally-trained embedding has stronger representation power. Experimental results show that the proposed embedding learning method achieves high precision regarding the task of expert finding.
To summarize, this thesis provides important results of low-rank estimation and embedding learning models for high-dimensional data analysis and real-world applications.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-08-01The student, Huan Gui, accepted the attached license on 2017-07-12 at 00:00.The student, Huan Gui, submitted this Dissertation for approval on 2017-07-12 at 00:08.This Dissertation was approved for publication on 2017-07-13 at 15:11.DSpace SAF Submission Ingestion Package generated from Vireo submission #11417 on 2017-09-29 at 11:19:04Made available in DSpace on 2017-09-29T16:39:46Z (GMT). No. of bitstreams: 3
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A Study on the Calligraphy of Gui Fu
No full textDuring the Qianlong-Jiaqing Era, there has been a rise in stele studies. Under the influence of highly-concerned textural studies and epigraphy, the calligraphic style in Qing dynasty became simple and unadorned with emphasis on archaism. Gui Fu (1736-1805), known as one of the 'four famous experts in Shuowen,' not only conducted academic research, but also investigated the inscriptions on ancient bronzes and stone tablets. Although his calligraphic and seal cutting works are not plenteous, the quantity is still impressive. All the time he is well-known for his clerical script, which served as a direct connection to Han dynasty. Gui Fu was imbued with conventional Confucianism and devoted his whole life to studying philology. The interaction between such circumstances and his penchant made his style simple, modest, and archaic. However, the specialized research on the calligraphy of Gui Fu is not given enough weight in recent time. Based on his significant accomplishment in academic research, as well as the sensible manner of a classics scholar revealed in his calligraphy art, the author therefore chose Gui Fu as the research topic.
The research purpose of this paper is to understand Gui Fu's learning procedure of calligraphy, to compare the different calligraphic style between his early and late periods, to relate the dated works with the undated and gauge the probable creation time for the undated works, and by predecessors' comments, to comprehend his artistic evaluation in the calligraphic development and history of Qing dynasty. The research methods adopted include documentary analysis and comparative analysis. Through a comprehensive collection of materials, analysis, summary, and a comparison between Gui Fu's calligraphic scripts and the Han steles that were imitated in his learning process, the author attempts to organize his bequeathed calligraphic scripts both in the early and late periods, and to summarize his various characteristics and calligraphic styles.
Gui Fu's accomplishments in clerical script art came from widely imitating the Han steles, from tracing back to antiquities, from carrying on the tradition of clerical script from Han dynasty, and from breaking away from the weird wavelike strokes and bizarre character structure. His profound knowledge consummated a unique point of view in calligraphy. His aesthetic perspective in clerical script can been seen especially in the 'Clerical Script Works of Qing Dynasty.'. Gui Fu's early and late calligraphic styles were distinguished by the age of 61; henceforth, the form of his whole characters became square, and his strokes came to be muscular, firm and rich. His archaic and vigorous calligraphic style revealed the active spirits of Confucianism, and formed a modest and profound personal style. In sum, Gui Fu is one of the main calligraphers of stele studies and clerical script in Qing dynasty.乾嘉之際，碑學興起，考據、金石受到高度關注的影響下，清代書風轉變為質樸尚古。桂馥（1736－1805）以「說文四大家」聞名於世，除了學術研究之外，研討金石碑版，於書法、篆刻方面雖然作品數量不豐，然頗有可觀，向來以隸著稱，其隸書直接漢人，受正統儒學薰染與畢生窮究小學，環境與嗜好的交互作用下造就其平實沉著的古樸之風。近來對於桂馥書法的專門研究並未受到重視，然以其在學術研究上的高度成就，書法藝術流露出經學家的理智氣度，因而選擇以桂馥作為此次研究主題。
本文研究目的在於了解桂馥書法學習歷程，比較桂馥前後期書風差異，將「紀年」與「未紀年」作品相互參照，判斷「未紀年」作品約略創作時期，藉由前人評價，了解他在清代書法發展史所在的藝術定位。研究方法採取文獻分析法與比較研究法，透過全面性的資料蒐集、分析彙整，再將桂馥書跡與學書歷程中所臨習漢碑對比，整理其前後時期傳世書跡，歸納出不同的特色與書風。
桂馥的隸書藝術成就來自廣泛臨寫漢碑，溯源古典，繼承漢隸的傳統，並且脫離清初以來詭異的波挑線條和怪異的結字架構，其深厚的學術涵養成就獨到的書法見解，尤於《國朝隸品》中可見其對隸書的審美觀點；六十一歲界分出前後期書風之差異，整體字形走向方正，而且用筆更為雄健渾厚，古樸遒健書風流露儒家積極精神，形成端莊厚重的個人風格，是清代碑學隸書的主要書家之一。桂馥書法研究
目次
第一章 緒論……………………………………………………………………………………1
第一節 研究動機與目的…………………………………………………………1
第二節 研究資料探討………………………………………………………………2
第三節 研究範圍、方法與限制………………………………………………4
第二章 桂馥家世生平與交遊 ……………………………………………………9
第一節 家世生平 ……………………………………………………………………………9
第二節 交遊 ……………………………………………………………………………15
第三章 桂馥與書法相關的學術研究…………………………………………25
第一節 桂馥與書法相關的文字學研究 ……………………………25
一、篆隸兼用古籀 …………………………………………………………………25
二、變形及訛混現象 ……………………………………………………………30
三、文字演變的規律 ……………………………………………………………36
第二節 桂馥與書法相關的金石學研究 ………………………………38
一、研討金石碑版 …………………………………………………………………41
二、考證文字變遷 …………………………………………………………………43
第三節 篆刻研究 ……………………………………………………………………47
一、師法秦漢，力主復古 ……………………………………………………47
二、篆刻成就 …………………………………………………………………………51
第四章 桂馥的學書歷程與書法言論…………………………………………57
第一節 書學淵源 ……………………………………………………………………57
一、取法漢碑 ………………………………………………………………………57
二、友人切磋 ………………………………………………………………………64
第二節 書法言論 ……………………………………………………………………67
一、書法言論 …………………………………………………………………………67
二、《國朝隸品》 …………………………………………………………………70
第五章 桂馥書法分期、特色與評價…………………………………………77
第一節 傳世作品書法分期………………………………………………………77
一、前期（61歲以前……………………………………………………………78
二、後期（61歲以後）…………………………………………………………90
第二節 桂馥書法特色 ……………………………………………………………97
一、筆法墨韻，淳古樸茂………………………………………………………97
二、結字布局，平實嚴謹………………………………………………………101
三、多元取法，兼容並蓄………………………………………………………105
四、書跡辨真 …………………………………………………………………………110
第三節 桂馥書法的評價…………………………………………………………114
一、正面評價…………………………………………………………………………114
二、負面評價…………………………………………………………………………116
第四節 桂馥在書法史之定位………………………………………………118
第六章 結論……………………………………………………………………………………125
參考書目……………………………………………………………………………………………127
附錄一 桂馥記年書法年表……………………………………………………………135
附錄二 桂馥未記年書法年表………………………………………………………13
Solutions to the First-order Buckling Equations of a Fung Hyperelastic Cylindrical Shell Subjected to Torsion, Internal Pressure, and Axial Tension
No full textThe author has granted permission for their work to be available to the general public.In this study a theoretical model is proposed for the buckling of a vein subjected to torsion, internal pressure, and axial tension using a formation of elasticity theory for shells. The vein is assumed to be an anisotropic hyperelastic cylindrical shell which obeys the Fung constitutive model.
The approach uses finite deformation theory for thick-walled blood vessels to characterize the vessel dilation in the pre-buckling state. The pre-buckling state is identified by its midpoint and then perturbed by a displacement vector field dependent on the circumferential and axial directions to define the buckled state. The buckling equations of static equilibrium are derived using the nominal stress measure and traction boundary conditions are applied. A side result is shown proving the existence of a moment traction although typically taken to be zero for torsional problems. Perturbational displacements raised to the power of two or greater are assumed negligible thereby linearizing the coupled partial differential equations of equilibrium. The coupled equations are solved by supposing first-order and single Fourier term trigonometric forms for the displacement field components.
The model and the assumptions used are validated by experimental data for five human great saphenous vein (GSV) samples taken from a previous study. The theoretical model is unstable but using an eigenvalue compatibility condition as a selection method yields strong quantitative results for three out of five GSVs in the entire tested pressure range (6-100 mmHg). The other two sampless showed excessive stiffening upon loading and may indicate limitations of the model although quantitative predictions were still moderately accurate. The strongest results are in the 6-20 mmHg pressure range where all vessels matched well with predicted values. In general the model showed increased error as pressure increased hinting that effects of vessel stiffening are poorly predicted. The eigenmodes predicted were consistently inaccurate indicating the assumptions used in this solution method are inadequate to characterize the buckling modes of a nonlinear material. It may suggest that nonlinear buckling conformation is determined by nonlinear perturbation terms.Biomedical Engineerin
Organocatalyzed Enantioselective Synthesis of α-Amino Acid Esters, β-Hydroxycarbonyl Compounds, Pyrano[2,3-b] Pyrans and α-Amino Acid Derivatives
No full textThe author has granted permission for their work to be available to the general public.Performing asymmetric transformations is one of the most challenging areas of organic chemistry. Most importantly, within a chiral surrounding, two enantiomeric biologically active agents often behave differently. Therefore, to develop an enantioselective synthesis of the desired enantiomer in an asymmetric transformation is highly desirable in medicinal chemistry as well as in the pharmaceutical industry. Over the last fifteen years the field of organocatalysis has grown from a small collection of unique or unusual chemical reactions to a thriving area of research with a very broad scope of reactions, and a typical reactivities and selectivities. It has now become a well established approach for asymmetric organic synthesis. This dissertation describes the highly enantioselective synthesis of versatile synthetic intermediates in the synthesis of a multitude of important chiral compounds. The organocatalysts used in this study are bifunctional and are capable of activation both the nucleophile and the electrophile simultaneously and frequently demonstrate superior reactivity and stereoselectivity. This dissertation work demonstrates that cinchona alkaloid-derived thioureas are superior organocatalysts for the synthesis of enantiomerically enriched biologically active molecules, such as α-amino acid esters or α-hydroxy acid esters and β-hydroxy carbonyl compounds. Organocatalysis is currently one of the fastest growing fields of research in organic chemistry. Catalysis by metal free organic molecules has been known in organic chemistry for more than 100 years, but its full potential was recognized only until the 21st century. Today, the most applications of organocatalysts are in asymmetric reactions. Development of new chiral catalysts is normally based on the structural tuning of known catalysts and on the synthesis of catalyst libraries. Catalyst development is a time consuming and complex process. The prediction of catalyst properties such as selectivity and reactivity is very difficult and the substrate scope of any given catalyst is usually narrow. Most of the reported organocatalysts have the reaction center moiety and the stereocontrolling moiety in the same molecule connected by covalent bonds. This design is highly effective in achieving stereocontrol, but is disadvantageous for the modification and fine tuning of catalyst structures. The aim of the thesis is to bridge the gaps in the catalyst synthesis, which is suitable for high throughput screening. We designed target organocatalyst in a simplified way, it is synthesized in-situ from the self-assembly of the precatalyst modules (proteogenic α-aminoacids and cinchona alkaloid derivatives) through ionic interactions. Enantioselectivity and reactivity may be fine-tuned to a substrate or specific reaction by simply replacing the modules, without the need of synthesizing new chiral catalysts.Chemistr
Images of the Han Chinese Reflected in the Oral Poetry of the Liang shan Yi
No full textVarious social phenomena are reflected in oral poetry, and so it is
very useful for understanding the society in which it was created. When
we are investigating how a matter is viewed by an ethnic group, the formulaic
phrases that we find in their oral poetry are valuable owing to
their very formulaic nature because the common, ordinary views of a
society can be embodied in those phrases.
By using Yi source materials, this paper describes and surveys the
formulaic phrases whose content can reflect how the Yi people living in
the Liang-shan district, Si-chuan, China, viewed the Han-Chinese in the
past. Then, based on the described images of the Han-Chinese, the
author examines how the Yi people saw ethnic relations with the Han-
Chinese.
The Yi are an ethnic minority mainly distributed over the provinces
of Si-chuan, Yun-nan, Gui-zhou and the Guang-xi Zhuang Autonomous
Region. There are about 1,500,000 Yi people in the Liang-shan district
now. The language spoken by the Yi belongs to the Tibeto-Burman
group.
Through research and examination, the author reached the following
conclusions:
(1) It is very probable that the period when the main images of the
Han-Chinese were formed to be reflected in Yi oral poetry ranges from
the Qing dynasty to the Kuomintang period. This conclusion is based
on the fact that there are phrases expressing opium, guns and the ornamental
gems on caps worn by Qing dynasty officers; it is also sup-
ported by the fact that the phenomena reflected in the oral poetry agree
with those reported in the ethnographies written by those who visited the
Liang-shan district at that period.
(2) The Han-Chinese were recognized as an ethnic group distinct
from the Liang-shan Yi themselves. Among the ethnic groups known to
the Liang-shan Yi, the Han-Chinese occupied their main interest.
(3) Two images of the Han-Chinese are especially conspicuous:
i) One is that of the Han-Chinese as the people in power. We can infer
this image from the formulaic expressions concerning Han-Chinese
officers accompanied by large armies. The Han-Chinese officers are also
associated with jails to put the Liang-shan Yi in. We can suppose that
the Liang-shan Yi felt themselves oppressed under the power of the Han-
Chinese officers supported by their overwhelming military force. The Yi
tried to keep a friendly relationship with the Han-Chinese officers while
they could get benefit from it. This makes it easy for us to understand
why the Liang-shan Yi did not hesitate to attack the Han-Chinese once
their power was weakened and the advantage of cooperation with them
was lost.
ii) Another image is that of the Han-Chinese as suppliers of commodities.
This image can be inferred from many formulaic expressions
concerning merchandise sold by the Han-Chinese merchants. It includes
articles such as salt, cotton cloth, liquor, candy, guns, pans, etc.
It is likely that the Liang-shan Yi were attracted by the affluence that the
Han-Chinese possessed. That affluence itself may have stimulated the
Yi to plunder the Han-Chinese.
4) In many formulaic phrases, political and economic activities are
associated with cities and streets where Han-Chinese lived. It is probable
that the cities located around the Liang-shan Yi district worked as an important
place of contact between the Han-Chinese and the Liang-shan
Yi.departmental bulletin pape
New and Efficient Approaches to Functionalization via Metal-Catalyzed and Photo-Induced Transformations
No full textThe author has granted permission for their work to be available to the general public.Functionalization has emerged as an attractive strategy for the diversification of compounds especially in drug development and materials science. The recent emerging trend in chemical functionalization is not only to access challenging and valuable compounds using abundant and inexpensive materials but also to consider environmental aspects of new methodologies. New methodologies in the fields of photocatalysis, transition metal catalysis, radical chemistry, and redox chemistry have found applications in functionalization. Herein, new and efficient approaches to functionalization of common aryl halides, abundant carboxylic acids, and readily available alkenes via metal-catalyzed or photoinduced transformations will be discussed. Specifically, the focus will be on the following transformations: conversion of aryl halides to borylated compounds and corresponding sulfones, as well as conversion of carboxylic acids to amines, alkenes, and other important compounds. Alkenes take part in discrete carboborative ring contractions or challenging dienes syntheses. In some cases, discussion of the mechanistic investigations and density functional theory calculations will be included to provide insights into the reaction details. Some ongoing works with preliminary results in decarboxylation and dienylation will be briefly discussed.Chemistr
GURU v2.0: An interactive Graphical User interface to fit rheometer curves in Han's model for rubber vulcanization
No full textA GUI software (GURU) for experimental data fitting of rheometer curves in Natural Rubber (NR) vulcanized with sulphur at different curing temperatures is presented. Experimental data are automatically loaded in GURU from an Excel spreadsheet coming from the output of the experimental machine (moving die rheometer). To fit the experimental data, the general reaction scheme proposed by Han and co-workers for NR vulcanized with sulphur is considered. From the simplified kinetic scheme adopted, a closed form solution can be found for the crosslink density, with the only limitation that the induction period is excluded from computations. Three kinetic constants must be determined in such a way to minimize the absolute error between normalized experimental data and numerical prediction. Usually, this result is achieved by means of standard least-squares data fitting. On the contrary, GURU works interactively by means of a Graphical User Interface (GUI) to minimize the error and allows an interactive calibration of the kinetic constants by means of sliders. A simple mouse click on the sliders allows the assignment of a value for each kinetic constant and a visual comparison between numerical and experimental curves. Users will thus find optimal values of the constants by means of a classic trial and error strategy. An experimental case of technical relevance is shown as benchmark
Electrical stimulation does not enhance nerve regeneration if delayed after sciatic nerve injury: the role of fibrosis
No full textElectrical stimulation has been shown to accelerate and enhance nerve regeneration in sensory and motor neurons after injury, but there is little evidence that focuses on the varying degrees of fibrosis in the delayed repair of peripheral nerve tissue. In this study, a rat model of sciatic nerve transection injury was repaired with a biodegradable conduit at 1 day, 1 week, 1 month and 2 months after injury, when the rats were divided into two subgroups. In the experimental group, rats were treated with electrical stimuli of frequency of 20 Hz, pulse width 100 ms and direct current voltage of 3 V; while rats in the control group received no electrical stimulation after the conduit operation. Histological results showed that stained collagen fibers comprised less than 20% of the total operated area in the two groups after delayed repair at both 1 day and 1 week but after longer delays, the collagen fiber area increased with the time after injury. Immunohistochemical staining revealed that the expression level of transforming growth factor β (an indicator of tissue fibrosis) decreased at both 1 day and 1 week after delayed repair but increased at both 1 and 2 months after delayed repair. These findings indicate that if the biodegradable conduit repair combined with electrical stimulation is delayed, it results in a poor outcome following sciatic nerve injury. One month after injury, tissue degeneration and distal fibrosis are apparent and are probably the main reason why electrical stimulation fails to promote nerve regeneration after delayed repair
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