医用生物材料的低温保存研究

生物材料的低温保存一般都要经历降温过程、低温储存过程及复温过程,其中降温过程中对生物细胞的影响最大.每一种生物细胞都有自己合适的降温速率,如能满足其这种降温速率,细胞所受到的低温损伤最小,则生物细胞的复活率最高.文中介绍程序控制变速降温装置的主要结构及几种典型生物体的降温过程.最后,对器官的低温保存进行分析讨论.     

生物材料低温保存过程及最新进展

介绍了生物材料低温保存所需经历的三个阶段,即降温过程、储存过程、复温过程。低温保护剂介入低温保存的全过程,这有助于提高生物材料低温保存的存活率,所以选择合适的低温保护剂也很重要。最后还介绍了低温保存的最新进展。     

生物材料低温保存过程中的温度场模拟

低温保存是生物材料进行长时间保存的一种有效方法,但在0℃~-60℃的温区范围,极容易发生低温损伤,如何减小低温损伤是细胞进行成功的低温保存的关键。文中建立了生物组织在低温保存过程中的数学模型,通过ANSYS分析软件,对样品在降温过程中的温度场进行了计算分析和数值模拟,为冷冻造成细胞损伤的研究提供了理论依据。     

液相线跟踪低温保存方法的研究

液相线跟踪法是生物材料玻璃化保存的一种手段。降温时通过边降温边提高低温保护剂浓度、复温时边升温边降低低温保护剂浓度的方式,该方法能够有效减轻降温/复温过程中高浓度保护剂对细胞的毒性损伤,从而提高生物材料低温保存的成活率。文中介绍可实现液相线跟踪的低温保存装置,该装置以液氮为冷源、采用计算机控制。以二甲亚砜-氯化钠-水溶液为例进行的实验表明,该装置能够实现温度和保护剂浓度的良好匹配,二甲亚砜的最终浓度达到了玻璃化所需浓度。     

生物材料低温保存设备的研究

介绍了生物材料低温保存设备的工作过程和装置结构,并对主要部件冷却室的结构和制作原理进行了分析,同时对控制系统及冷冻速率进行讨论。     

降温速率对低温保存动脉粘弹性的影响

使用DMA测定了3种降温速率低温保存的家兔颈总动脉的蠕变曲线.结果表明:1.5℃/min降温速率低温保存后,血管的粘弹性最接近新鲜对照组;而对应降温速率1.5,5,10℃/min,血管粘弹性依次降低.动脉的粘弹性极有可能是评估其低温保存效果的潜在评价指标.     

生物材料玻璃化保存液的热分析

在玻璃化超低温保存生物材料的研究中,低温保护剂的热分析对玻璃化溶液的优化和保存方案的选择具有重要的指导意义.本文以渗透性低温保护剂二甲基亚砜和丙二醇以及非渗透性保护剂聚乙烯醇作为研究对象,利用差式扫描量热法对聚乙烯醇/二甲基亚砜/丙二醇体系进行升温和降温实验,考察了体系的结晶特性、玻璃化转变特性、聚乙烯醇的浓度等因素对体系热性能参数的影响.     

生物材料冻存中低温保护剂的作用机理及实验研究

生物材料在冻存过程中保存液内加载低温保护剂可以减轻降温和复温时对细胞的损伤。介绍了低温保护剂的种类及其特点,分析了低温保护剂的作用机理。实验结果表明,选择合适的低温保护剂及其浓度,可以大大提高生物细胞的存活率。     

细胞尺度冰晶生长行为的相场数值模拟

细胞尺度的冻结损伤机制是实施低温手术及生物材料低温保存的关键,本文围绕低温条件下的微尺度冻结问题,应用相场模型对冰晶的形成过程进行了数值模拟,明确了相场模型相关重要参数的确定方法,并最终得到各向同性条件下,二维平面内冰晶的生长过程及其生长特点.     

基于薄液膜蒸发的超高速冷冻方法初探

玻璃化冷冻方法是细胞超低温保存的有效冷冻方法之一.在细胞的玻璃化冷冻过程中,降温速率的提高有利于细胞内外溶液玻璃化程度的增加,同时可以降低低温保护剂的浓度,进而减少低温保护剂对细胞的毒性损伤和渗透性损伤.本文尝试将薄液膜蒸发这种高效相变传热方式与液氮的低温冷却过程相结合,发展了一种超高速、超低温冷冻降温方法.初步的实验结果表明:冷冻载体从10℃降到-180℃,其平均冷却速率达到了148052℃/min。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.