駢文韻律與超時空語法 : 以《蕪城賦》爲例

“駢文”得名於文章排句之方式、“四六文”得名於造句之字數。漢魏以降，駢文儷偶便成爲中國古典文學的一個重要文體。理論上説，文學語言、文體形式均根植於該語言的語法機制。然而，爲什麽駢文句式要四六？四六的拼搭有何必然？四六之美何在？駢文離開“四”和“六”還是不是“駢文”？此類問題仍然有待回答，本文即探討這方面問題的一個嘗試

Optimal trajectory control of series resonant converter

Resonant power converters have gained increased attention in industry due to various advantages over conventional pulse width modulation (PWM) converters. Resonant converters have improved transient response, reduced switching losses and stresses, reduced equipment size and weight and reduced electromagnetic interference (EMI). In this thesis, series resonant converters (SRC) in variable and constant frequency topologies are analyzed using state-space approach for effective control. The design and implementation of a practical optimal trajectory control (OTC) scheme is shown. Experimental results are presented to demonstrate the performance of the proposed control scheme

Influence of substrate on corneal epithelial cell viability within ocular surface models

Corneal tissue engineering has improved dramatically over recent years. It is now possible to apply these technological advancements to the development of superior in vitro ocular surface models to reduce animal testing. We aim to show the effect different substrates can have on the viability of expanded corneal epithelial cells and that those which more accurately mimic the stromal surface provide the most protection against toxic assault. Compressed collagen gel as a substrate for the expansion of a human epithelial cell line was compared against two well-known substrates for modeling the ocular surface (polycarbonate membrane and conventional collagen gel). Cells were expanded over 10 days at which point cell stratification, cell number and expression of junctional proteins were assessed by electron microscopy, immunohistochemistry and RT-PCR. The effect of increasing concentrations of sodium lauryl sulphate on epithelial cell viability was quantified by MTT assay. Results showed improvement in terms of stratification, cell number and tight junction expression in human epithelial cells expanded upon either the polycarbonate membrane or compressed collagen gel when compared to a the use of a conventional collagen gel. However, cell viability was significantly higher in cells expanded upon the compressed collagen gel. We conclude that the more naturalistic composition and mechanical properties of compressed collagen gels produces a more robust corneal model

Performance analysis and comparison of PoW, PoS and DAG based blockchains

In the blockchain, the consensus mechanism plays a key role in maintaining the security and legitimation of contents recorded in the blocks. Various blockchain consensus mechanisms have been proposed. However, there is no technical analysis and comparison as a guideline to determine which type of consensus mechanism should be adopted in a specific scenario/application. To this end, this work investigates three mainstream consensus mechanisms in the blockchain, namely, Proof of Work (PoW), Proof of Stake (PoS), and Direct Acyclic Graph (DAG), and derives their performances in terms of the average time to generate a new block, the confirmation delay, the Transaction Per Second (TPS) and the confirmation failure probability. The results show that the consensus process is affected by both network resource (computation power/coin age, buffer size) and network load conditions. In addition, it shows that PoW and PoS are more sensitive to the change of network resource while DAG is more sensitive to network load conditions

Optical inhibition of motor nerve and muscle activity

Introduction: There is no therapeutic approach that provides precise and rapidly reversible inhibition of motor nerve and muscle activity for treatment of spastic hypertonia. Methods: We used optogenetics to demonstrate precise and rapidly reversible light-mediated inhibition of motor nerve and muscle activity in vivo in transgenic Thy1::eNpHR2.0 mice. Results: We found optical inhibition of motor nerve and muscle activity to be effective at all muscle force amplitudes and determined that muscle activity can be modulated by changing light pulse duration and light power density. Conclusions: This demonstration of optical inhibition of motor nerves is an important advancement toward novel optogenetics-based therapies for spastic hypertonia.Stanford University (Stanford Bio-X Interdisciplinary Initiatives Award)Stanford University (National Institutes of Health Graduate Training Program in Biotechnology grant)W. M. Keck Foundation (grant)National Institutes of Health (U.S.) (NIH grant R01NS080954

Prevalence and risk factors of hepatitis C among former blood donors in rural China

SummaryBackgroundIllegal commercial plasma and blood donation activities in the late 1980s and early 1990s caused a large number of hepatitis C virus (HCV) infections in rural areas of China.MethodsA cross-sectional survey was carried out in 2008, in which all residents in a former blood donation village in rural Hebei Province were invited for a questionnaire interview and testing for HCV antibodies. Questionnaires were administered to collect information about their personal status and commercial blood donation history, and HCV antibodies were tested by enzyme immunoassay.ResultsOf 520 villagers who participated in the interviews, 236 (45.4%) reported a history of selling whole blood or plasma. HCV seropositivity was confirmed in 148/520 (28.5%) interviewees and 101/236 (42.8%) former commercial plasma and blood donors. Selling plasma was the strongest independent predictor of HCV seropositivity (p=0.0037). Past history of an operation was also independently associated with HCV infection (p=0.0270).ConclusionsUnsafe practices during illegal plasma donation led to a high risk of HCV seropositivity for donors during the late 1980s and early 1990s. Many infected people suffered chronic hepatitis from that time onwards and urgently needed treatment and care

Physical state of water controls friction of gabbro-built faults

: Earthquakes often occur along faults in the presence of hot, pressurized water. Here we exploit a new experimental device to study friction in gabbro faults with water in vapor, liquid and supercritical states (water temperature and pressure up to 400 °C and 30 MPa, respectively). The experimental faults are sheared over slip velocities from 1 μm/s to 100 mm/s and slip distances up to 3 m (seismic deformation conditions). Here, we show with water in the vapor state, fault friction decreases with increasing slip distance and velocity. However, when water is in the liquid or supercritical state, friction decreases with slip distance, regardless of slip velocity. We propose that the formation of weak minerals, the chemical bonding properties of water and (elasto)hydrodynamic lubrication may explain the weakening behavior of the experimental faults. In nature, the transition of water from liquid or supercritical to vapor state can cause an abrupt increase in fault friction that can stop or delay the nucleation phase of an earthquake