植物暗适应叶的放氧动力学(Ⅰ)——光声放氧动力学

用光声光谱仪检测结果表明 ,暗适应叶在光诱导期间出现非常复杂的光声瞬态放氧 ,产生了一种称为氧峰(oxygengush)的现象 .该文利用自制的光声仪对暗适应菠菜叶在光诱导期间出现的光声瞬态放氧与暗适应时间关系 ,远红光、饱和光预处理以及高浓度CO2 对光声瞬态放氧的影响 ,光声热信号与光声放氧信号之间的关系作了初步研究 .推测由两个组分组成的氧峰与其动力学可能反映光系统Ⅱ的状态     

微波-活性炭去除垃圾渗滤液中CODcr的研究

采用微波-活性炭联合作用去除垃圾渗滤液中CODcr.通过正交设计,探讨活性炭用量、pH值、水样初始CODcr值、微波功率、辐照时间、搅拌时间6个因素对CODcr去除率的影响.结果表明在PAC用量5g,pH值为9,水样稀释1倍,微波强度为420W,辐照时间为4min,搅拌时间为45min时处理的效果最好,此时CODcr去除率可这83.12%.微波辐照能改变活性炭的结构,并正在表面产生一些高温"热点",这些"热点"是导致有机污染物降解的根本原因.     

基于小波分形的电能质量暂态扰动多分辨率分析

电能质量暂态扰动会给敏感负荷带来重大损失.采用小波变换的多分辨率分析思想,利用分形理论从图形模式辨识的角度出发对电能质量暂态扰动进行分类、辨析.首先采用计算简单的计盒维数对波形图像进行初步分析,随后根据盒的分布密度进行分段划分,将含暂态扰动的信息段从波形中提取出来,并根据多分辨率分析的思想对重点波形段进行分形及小波分析提取信号特征.仿真结果证明,该方法对电能质量扰动的暂态识别具有较好的适应性及稳健性,可以在噪声环境下识别小幅度的电能质量扰动,具有检测速度快、可并发执行的特点.     

Convective and Microwave Drying Characteristics of Dill Leaves （Anethum graveolens L.）

In this research, convective and microwave drying characteristics, energy requirement and color changes of dill leaves （Anethum graveolens L.） were reported. Dill leaves were dehydrated in a computer connected parallel air flow type dryer and in a microwave oven dryer. Samples of freshly harvested dill leaves were dehydrated under three air temperatures of 50, 60 and 70 ℃, and at three microwave power levels of PL-1 （90 W）, PL-2 （160 W） and PL-3 （350 W）. Selected drying air velocity was 0.30 m/s for all temperatures. Dill leaves were dehydrated from the initial moisture content of 735 （percentage dry basis） to a final moisture content of 8%-10%. During convective drying experiment, products were weighted automatically by the balance per 5-10 min. Data were transferred to the computer and processed by software. During microwave drying, the products were weighted, and data were recorded manually per 15-60 min. The influence of drying method, drying air temperature and microwave power level has also been studied. Hunter L, a, b values system was also used to evaluate changes in total color difference （AE） on dried products. The results showed that convective drying air temperature and microwave oven power levels influenced the total drying time, total energy requirement, specific energy requirement and color difference for dill leaves. The minimum specific energy requirement was determined as 10.72 kWh/kg and 18.72 kWh/kg for 70 ℃ and PL-3, respectively. 70℃ drying air temperature and PL-3 were found to yield better quality product in terms of color retention of Hunter L, a, b and AE. As a result, to reduce drying energy consumption and to keep better color retention, convective drying can be recommended for this application.     

Behavioral sensitivity to microwave irradiation

In "Behavioral sensitivity to microwave irradiation" by N. W. King et al. (23 Apr., p. 398), lines 1 to 8, coltumn 2, page 399, should read " basis of the level of focusing current used to control and monitor the output power of the magnetron (25). A shift from zero to a present level of available power in the exposure cavity was accomplished by applying 5 kv of 60-hz a-c voltage to the anode of the magnetron."     

Clusters of hyperactive neurons near amyloid plaques in a mouse model of Alzheimer's disease

The neurodegeneration observed in Alzheimer's disease has been associated with synaptic dismantling and progressive decrease in neuronal activity. We tested this hypothesis in vivo by using two-photon Ca2+ imaging in a mouse model of Alzheimer's disease. Although a decrease in neuronal activity was seen in 29% of layer 2/3 cortical neurons, 21% of neurons displayed an unexpected increase in the frequency of spontaneous Ca2+ transients. These "hyperactive" neurons were found exclusively near the plaques of amyloid beta-depositing mice. The hyperactivity appeared to be due to a relative decrease in synaptic inhibition. Thus, we suggest that a redistribution of synaptic drive between silent and hyperactive neurons, rather than an overall decrease in synaptic activity, provides a mechanism for the disturbed cortical function in Alzheimer's disease.     

The Possibilities of Bioenergy Production from Whey

The wastes and the by-products of food industrial technologies are suitable for bioenergy generating because of the high organic matter content. Anaerobic digestion is the eldest technology for waste stabilization and however by controlled decomposition a high value and marketable energy source can be produced. Whey is normally used as a component of dairy products or as an additive for food product. In our work we focused on another utilization method： biogas generating from membrane separated fractions i.e.： permeate and concentrate of whey. The effect of the pH, thermal, microwave pre-treatment and their combinations on the biogas yield were investigated. Our results showed that the applied pre-treatments had significant effect on biogas production. In consequence of the hydrolysis of large molecules the biodegradability of the pre-treated whey fractions was enhanced, therefore the biogas and methane production yield increased significantly.     

Man-made transients observed by the gamma-ray spectrometer on the solar maximum mission satellite

Since launch in early 1980 the Gamma-Ray Spectrometer (GRS) onboard the Solar Maximum Mission (SMM) satellite has monitored the sun at gamma-ray energies. In addition to observations of solar flares, cosmic gamma-ray bursts, and precipitating radiation belt electrons, the instrument has detected a new class of high-energy transient events that cannot be attributed to any of these phenomena. The duration of these transients can range from 1 second to more than 10 minutes. The average event rate between 1980 and 1986 was about five per month. However, in February 1987 this rate increased by more than a factor of 25 and continued at this high level until June 1988. These transients can be subdivided into three classes: (i) 0.511-megaelectron volt annihilation line events, (ii) particle events, and (iii) broad-band photon continuum-like events. Evidence is presented that these transients are not of natural origin. It is found that the most likely sources of these events are reactors in earth orbiting satellites. Apart from the threat these reactors pose upon accidental reentry, the reactor-generated transients may have a deleterious effect on cosmic observations obtained with gamma-ray detectors in low earth orbit.     

微波干燥过程中木材内部水分移动机理初探

该文通过测定木材微波干燥过程中内部的温度、压力和分层含水率,着重研究了在微波干燥过程中木材内部温度、水蒸气压力和水分分布状态与变化情况.通过对其相互关系的理论分析,得出了以下研究结果:在微波干燥过程中,木材内的温度分布比较均匀,但在干燥的后期,木材内温度分布的不均匀性有加大的趋势;随着干燥的进行,木材内部含水率梯度逐渐减小,含水率分布更加均匀;在木材干燥的初期,木材表面有水分“积聚”现象;在功率1000W条件下,测定规格300mm×100mm×60mm试材内部压力,纤维长度方向木材内部最大压差为20.1kPa,厚度方向木材内部最大压差为17.9kPa,表明木材微波干燥过程中在厚度和长度方向分别存在明显的蒸汽压力梯度.     

原子吸收法测定彝药见肿消中微量元素的含量

[目的]探明彝药见肿消中微量元素的含量。[方法]采用火焰原子吸收光度法进行测定分析,用浓硝酸微波消解样品,采用标准曲线法计算。[结果]彝药见肿消中的钙、镁、铁、锌、铜、锰的质量分数分别是19.970、8.500、1.110、0.043、0.400、0.043 mg/g,RSD为2.5%～9.7%,加标回收率在95%～102%之间。[结论]该方法简单,测定结果准确。     

液体弹性波在管输系统中的应用

根据液体弹性波在管道中的传输特性,结合原油管输系统,提出了刊用弹性波振荡和水击效应来防蜡防垢、排污解堵,从而实现降耗节能安全输油的新思路。针对水击压力波的产生及传播特性,指出该技术方案的本质是水击(锤)反问题及水击(锤)控制。介绍了国内外有压瞬变流的研究动态及现状,探讨了尚待研究的理论及问题。     

Tension transients in single isolated smooth muscle cells

Tension transients were recorded in a single smooth muscle cell. The transient contains a linear elastic response and a biphasic recovery that appear to originate from the cross-bridges. A comparison of transients in smooth and fast skeletal muscle fibers suggests that the cross-bridge in smooth muscle is more compliant than the cross-bridge in striated muscle and that transitions between several cross-bridge states occur more slowly in smooth muscle than in striated muscle.     

刨花微波干燥特性研究

研究了常规微波干燥、热空气干燥、微波-热空气联合干燥下刨花含水率和干燥速率的变化特征,微波功率和刨花形态对含水率变化和干燥速率等特性的影响,计算了刨花在微波干燥下的单位能耗.结果表明:微波干燥比热空气干燥省时约80%;微波功率对干燥特性有显著影响,功率越大,干燥速率越快,干燥时间也越短;微波干燥过程中,刨花形态对干燥速率有影响,表面积越大的刨花,含水率变化越明显,干燥速率越快;微波输出功率与试样量比为4~7W/g时,微波能耗最省;微波干燥过程中易发生能量集中而导致刨花焦化,微波-热空气联合干燥可以防止焦化现象,同时能实现更低的目标含水率,微波-热空气联合干燥比热空气干燥省时约70%.     

不同微波条件下烟叶微观结构的变化

[目的]深入研究微波对烟叶组织结构的影响。[方法]采用扫描电子显微镜技术,比较不同功率微波处理后烟叶微观结构的细致变化。[结果]微波处理可以使烟叶内部组织结构发生有效的膨胀;当微波功率0.6 W/g时烟叶膨胀率随微波功率的增加而增大,当微波功率0.6 W/g时烟叶膨胀率趋于稳定;微波处理还对烟叶的导管纤维束等内部组织带来不同程度地破坏,从而影响烟叶的燃烧等化学性能。[结论]该研究为微波工艺在烟草应用中的工艺和加工条件优化等方面提供了参考。     

污泥提取蛋白的微波改性工艺条件研究

[目的]利用微波改性方法对起泡性能进行研究,以改善污泥提取蛋白的功能特性。[方法]以啤酒厂经过脱水压滤后的泥饼为剩余污泥样品,采用微波技术对污泥提取蛋白进行物理改性。通过单因素试验,研究微波功率、微波时间和蛋白质量分数对污泥蛋白起泡性的影响,得出最佳影响范围,然后通过正交试验,确定得出微波提高污泥蛋白的最佳工艺条件。[结果]正交试验方差分析表明,各因素对污泥蛋白起泡性的影响依次为蛋白质量分数>微波功率>微波时间;微波提高污泥蛋白的最佳条件为:微波时间3 min、微波功率540 W、蛋白质量分数5%。在此条件下,污泥提取蛋白的起泡性能和起泡稳定性分别提高53.8%和76%。[结论]改性后的污泥蛋白液在起泡性和起泡稳定性方面均有很大提高。     

微波膨化苹果脆片的响应曲面法优化分析

【目的】对微波膨化苹果脆片进行响应曲面法优化分析,以获得其优质、高效生产技术。【方法】以红富士苹果为试材,对预干燥后的苹果片进行微波膨化,探讨切片厚度、含水量、膨化时间和微波功率4因素及其交互作用对苹果脆片膨化率的影响,并采用响应曲面法对各影响因素进行优化分析。【结果】切片厚度、膨化时间和微波功率对苹果脆片膨化率影响显著,膨化时间和微波功率的交互作用对膨化率影响显著;微波膨化苹果脆片的最佳工艺条件为：切片厚度6mm,含水量18％,微波功率中档,膨化时间30．0s。【结论】采用响应曲面法可以优化微波膨化苹果脆片生产工艺,只要掌握适宜的切片厚度、微波功率及膨化时间,就能获得质地和风味俱佳的苹果脆片。     

Postsynaptic Induction of BDNF-Mediated Long-Term Potentiation

Brain-derived neurotrophic factor (BDNF) and other neurotrophins are critically involved in long-term potentiation (LTP). Previous reports point to a presynaptic site of neurotrophin action. By imaging dentate granule cells in mouse hippocampal slices, we identified BDNF-evoked Ca2+ transients in dendrites and spines, but not at presynaptic sites. Pairing a weak burst of synaptic stimulation with a brief dendritic BDNF application caused an immediate and robust induction of LTP. LTP induction required activation of postsynaptic Ca2+ channels and N-methyl-d-aspartate receptors and was prevented by the blockage of postsynaptic Ca2+ transients. Thus, our results suggest that BDNF-mediated LTP is induced postsynaptically. Our finding that dendritic spines are the exclusive synaptic sites for rapid BDNF-evoked Ca2+ signaling supports this conclusion.     

Signaling of rat Frizzled-2 through phosphodiesterase and cyclic GMP

The Frizzled-2 receptor (Rfz2) from rat binds Wnt proteins and can signal by activating calcium release from intracellular stores. We show that wild-type Rfz2 and a chimeric receptor consisting of the extracellular and transmembrane portions of the beta2-adrenergic receptor with cytoplasmic domains of Rfz2 also signaled through modulation of cyclic guanosine 3',5'-monophosphate (cGMP). Activation of either receptor led to a decline in the intracellular concentration of cGMP, a process that was inhibited in cells treated with pertussis toxin, reduced by suppression of the expression of the heterotrimeric GTP-binding protein (G protein) transducin, and suppressed through inhibition of cGMP-specific phosphodiesterase (PDE) activity. Moreover, PDE inhibitors blocked Rfz2-induced calcium transients in zebrafish embryos. Thus, Frizzled-2 appears to couple to PDEs and calcium transients through G proteins.     

微波膨化苹果脆片的响应曲面法优化分析

【目的】对微波膨化苹果脆片进行响应曲面法优化分析,以获得其优质、高效生产技术。【方法】以红富士苹果为试材,对预干燥后的苹果片进行微波膨化,探讨切片厚度、含水量、膨化时间和微波功率4因素及其交互作用对苹果脆片膨化率的影响,并采用响应曲面法对各影响因素进行优化分析。【结果】切片厚度、膨化时间和微波功率对苹果脆片膨化率影响显著,膨化时间和微波功率的交互作用对膨化率影响显著;微波膨化苹果脆片的最佳工艺条件为：切片厚度6 mm,含水量18%,微波功率中档,膨化时间30.0 s。【结论】采用响应曲面法可以优化微波膨化苹果脆片生产工艺,只要掌握适宜的切片厚度、微波功率及膨化时间,就能获得质地和风味俱佳的苹果脆片。     

Modifying the ionosphere with intense radio waves

The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications.