植物青枯病菌环介导等温扩增快速检测技术研究

为实现植物青枯病的早期诊断,需要建立一种适于田间快速便捷检测青枯病菌的方法。以细胞色素C基因为靶标设计一套特异性引物,建立了植物青枯病的LAMP检测方法。此方法最低检测极限为1 pg,可在1 h内完成,不依赖昂贵复杂的仪器,结果可经肉眼观察。利用此方法,在人工接种发病的茄子、番茄、花生、芝麻和凹头苋茎部浸出液和马铃薯病薯块茎组织液中均检测出青枯病菌的存在,尤其适用于田间疑似罹病的芝麻、花生、番茄、马铃薯和甘薯等植株的检测,且LAMP法的检出率远高于PCR法。应用LAMP技术检测青枯病菌快速高效、特异性强、灵敏度高,操作简单,适于在基层推广运用。     

The method for studying of the "magnetic vacuum" effect on color memory in humans

The method for studying the effects of weak magnetic fields and "magnetic vacuum" on the psychophysiological state of a human organism is proposed. This method includes the system of the exposure of a human organism to uniform constant and alternating magnetic fields and the system of computerized psychological tests. The influence of the weakening of constant magnetic field on the psychophysiological state of human organisms was studied. The short-term color memory and reaction rates of 30 subjects have been examined in the local geomagnetic field and in a magnetic field which was reduced in 10 and more times. Statistically significant differences in the color memory test was found in the magnetic field 4 +/- 1 microT in comparison with the results in the geomagnetic field. In the magnetic field 0 +/- 1 microT, slight impairment of color memory was found. Preliminary results in the test of reaction rates showed the tendency to slowing down the reaction rates in the weakened magnetic fields.     

Retinal Vessel Width Measurement at Branchings Using an Improved Electric Field Theory-Based Graph Approach

The retinal vessel width relationship at vessel branch points in fundus images is an important biomarker of retinal and systemic disease. We propose a fully automatic method to measure the vessel widths at branch points in fundus images. The method is a graph-based method, in which a graph construction method based on electric field theory is applied which specifically deals with complex branching patterns. The vessel centerline image is used as the initial segmentation of the graph. Branching points are detected on the vessel centerline image using a set of detection kernels. Crossing points are distinguished from branch points and excluded. The electric field based graph method is applied to construct the graph. This method is inspired by the non-intersecting force lines in an electric field. At last, the method is further improved to give a consistent vessel width measurement for the whole vessel tree. The algorithm was validated on 100 artery branchings and 100 vein branchings selected from 50 fundus images by comparing with vessel width measurements from two human experts.     

Intracellular recording during magnetic field application to monitor neurotransmitter release events: methods and preliminary results

A method for simultaneous magnetic field application and intracellular recording is presented. A little used method for magnetic field application was exploited; the field generator consisted of a flat copper sheet through which current was passed to generate a magnetic field. The resultant magnetic field was relatively homogeneous, exhibiting a variation of +/- 5%. This compact, current-sheet field generator was mounted on the condensor of a microscope. The current induced in the intracellular electrode was reduced by injecting current equal and opposite to the induced current into the microelectrode. This step reduces the possibility of cellular effects and voltage artifacts due to the induced electrode current. The technique was used to conduct preliminary studies on the effects of extremely low frequency (ELF) linearly and circularly polarized magnetic fields (1.0 Gauss, 60 and 70 Hz) on miniature end plate potential (mepp) frequency (frequency of neurotransmitter release events) of rat flexor digitorum brevis muscle. The same synapse was utilized for both the sham-exposed control and the exposed experimental halves of an experiment. After 10 min of exposure to a 60-Hz linear field, mepp frequency was significantly increased by 12%, but exposure to a 60-Hz circular field did not significantly alter mepp frequency. Exposure to a 70-Hz linear field did not significantly change mepp frequency, but application of a 70-Hz circular field appears to decrease mepp frequency by 4%. These results indicate that both types of magnetic fields can alter mepp frequency, depending upon the frequency and configuration of the field.     

Left ventricle motion estimation for cine MR images using sparse representation with shape constraint

Purpose: To propose a left ventricle (LV) motion estimation method based on sparse representation, in order to handle the spatial-varying intensity distortions caused by tissue deformation. Methods: For each myocardial landmark, an adaptive dictionary was generated by learning transformations from a training dataset. Then the landmark was tracked using sparse representation. Next, a point distribution model was applied to the overall tracking results. Finally, the dense displacement field of the LV myocardium was estimated based on the correspondence between each landmark. Using the dense displacement field estimated, the circumferential strain was calculated to assess the myocardial function. The performance of the proposed method was quantified by the average perpendicular distance (APD), the Dice metric, and the mean symmetric contour distance (SCD). Results: Comparing to the state-of-the-art techniques, the smallest value of APD and SCD, and the highest value of Dice can be obtained using the proposed method, for three public cardiac datasets. Moreover, the mean value of strain difference between the proposed method and the commercial software Medis Suite MR was −0.01, while the intraclass correlation coefficient between these two methods was 0.91. Conclusions: The proposed method could estimate the dense displacement field of the LV accurately, which outperforms other state-of-the-art techniques. The circumferential strain derived from the proposed method was in excellent agreement with that derived from the Medis Suite MR software, while segmental strain abnormalities were detected for most of the subjects with heart diseases, which indicates the potential of the proposed method for clinical usage.     

Genetic diversity of Bradyrhizobium japonicum field population revealed by RAPD fingerprinting

RAPD fingerprinting was used for strain identification and the assessment of genetic diversity within a field population of Bradyrhizobium japonicum . Total genomic DNAs from 13 field isolates and two inoculant strains were amplified using six different 10-mer primers. Different and informative band patterns were obtained for all strains analysed. Cluster analysis unexpectedly revealed that none of the field isolates was identical to inoculant strains which were regularly used for soybean inoculation. Among field isolates two highly divergent groups were determined. The results indicate that RAPD is a very discriminative and efficient method for differentiating and studying genetic diversity of B. japonicum strains.     

Duration of gut passage and its dependence on temperature and food consumption in roach, Rutilus rutilus L: laboratory and field experiments

A laboratory method is described by means of which gut passage time as a function of temperature, diet and consumption rate is investigated in roach, an omnivorous cyprinid. Rates of food passage are accelerated by increasing temperature and food consumption. Equations for the regressions between gut passage time and consumption rate at four temperatures are given. Animal food causes a delay in gut passage time. In adult roach (30-100 g body weight) gut passage time was found to be independent of size.
A field method was also developed which allows the direct estimation of gut passage time and consumption rate in natural fish populations. The results of experiments with this field method agree with those of laboratory experiments.     

A precise analytical method for calculating the electrostatic energy of macromolecules in aqueous solution

A new method for calculating the total electrostatic free energy of a macromolecule in solution is presented. It is applicable to molecules of arbitrary shape and size, including membranes or macromolecular assemblies with substrate molecules and ions. The method is derived from integrating the energy density of the electrostatic field and is termed the field energy method. It is based on the dielectric model, in which the solute and the surrounding water are regarded as different continuous dielectrics. The field energy method yields both the interaction energy between all charge pairs and the self energy of single charges, effectively accounting for the interaction with water. First, the dielectric boundary and mirror charges are determined for all charges of the solute. The energy is then given as a simple function of the interatomic distances, and the standard atomic partial charges and volumes. The interaction and self energy are shown to result from three-body and pairwise interactions. Both energy terms explicitly involve apolar atoms, revealing that apolar groups are also subject to electrostatic forces. We applied the field energy method to a spherical model protein. Comparison with the Kirkwood solution shows that errors are within a small percentage. As a further test, the field energy method was used to calculate the electrostatic potential of the protein superoxide dismutase. We obtained good agreement with the result from a program that implements the numerical finite difference algorithm. The field energy method provides a basis for energy minimization and dynamics programs that account for the solvent and screening effect of water at little computational expense.     

Ex Vivo and In Silico Feasibility Study of Monitoring Electric Field Distribution in Tissue during Electroporation Based Treatments

Magnetic resonance electrical impedance tomography (MREIT) was recently proposed for determining electric field distribution during electroporation in which cell membrane permeability is temporary increased by application of an external high electric field. The method was already successfully applied for reconstruction of electric field distribution in agar phantoms. Before the next step towards in vivo experiments is taken, monitoring of electric field distribution during electroporation of ex vivo tissue ex vivo and feasibility for its use in electroporation based treatments needed to be evaluated. Sequences of high voltage pulses were applied to chicken liver tissue in order to expose it to electric field which was measured by means of MREIT. MREIT was also evaluated for its use in electroporation based treatments by calculating electric field distribution for two regions, the tumor and the tumor-liver region, in a numerical model based on data obtained from clinical study on electrochemotherapy treatment of deep-seated tumors. Electric field distribution inside tissue was successfully measured ex vivo using MREIT and significant changes of tissue electrical conductivity were observed in the region of the highest electric field. A good agreement was obtained between the electric field distribution obtained by MREIT and the actual electric field distribution in evaluated regions of a numerical model, suggesting that implementation of MREIT could thus enable efficient detection of areas with insufficient electric field coverage during electroporation based treatments, thus assuring the effectiveness of the treatment.     

The crown-gap ratio (C) and crown cover: The field study

Crown cover can be used to describe or classify woody vegetation. However, current methods for the estimation of crown cover are difficult to apply and are time-consuming. The objective of this work was to present a much easier method of field estimation and to define the limitations of the method. The method uses the crown-gap ratio (C), which is defined as the mean gap between crowns divided by the mean crown diameter. The relationship between values for the crown-gap ratio and crown cover is of the form crown cover = k/(1 + C)², where k is a constant. The overall tasks are first, to develop a methodology to obtain estimates of C and crown openness in the field, and second, to estimate k. In Part 1 we demonstrate that crown cover can be related to C when applied to woody vegetation. In Part 2 we consider a derivation of C, determine a value for k given a set of constraints, and outline some of the sampling implications of applying the method of crown cover estimation using C and k to field situations. The field study provided data from which to plot crown cover against the crown-gap ratio (C). The shape of the curve approximated a rectangular hyperbola. The regression of crown cover against 1/(1 + C)² showed a strong linear relationship (R²= 0.995) and gave an estimate for k of 0.79 for the range of plant communities sampled. The field study suggests that to investigate the effect of different spatial distributions of crowns and mixtures of crown sizes on C, a rigorous derivation of the relationship between crown cover and C is required.     

Evaluation of the Single Tillers Method for Yield Loss Assessment in Wheat Under Israeli Conditions

A method for estimating disease induced yield losses by using single wheat tillers as experimental units was evaluated under commercial field conditions. Natural epidemics of Septoria tritici blotch, yellow rust and leaf rust which developed late in the season had no effect on the vegetative growth of the host, but caused only reduced kernels weight. The optimal sample size was determined experimentally to be 300 tillers. Losses were also estimated in the same experiments using field plots as experimental units. Yield loss estimates derved from using single tillers were significantly correlated with those derived from using field plots. The relationship between disease and yield varied significantly among fields, even in a given year, region and cultivar. Thus, it was concluded that this relationship has to be established empirically wherever yield losses are to be estimated, and that under Israeli conditions it may be done by using the single tillers method.     

麦圆蜘蛛在麦株上的转移习性观察

麦圆蜘蛛Penthaleus major(Duges)在小麦上的危害有明显加重的趋势,田间种群密度的调查仍是目前虫情测报的主要手段。为了解麦圆蜘蛛在麦株上的转移习性,以便为其田间调查取样和防治提供参考,作者于2008年进行3部分田间观察。结果表明:麦圆蜘蛛在小麦植株上具有较强的活动性,可随田间环境条件的不同而改变其栖息场所。在同一观察日内,其在麦株上的虫量多表现早晚时段多于中午时段;在有风、阴雨和气温相对较高时,麦株上的虫量分布均有明显下降的趋势。麦圆蜘蛛主要分布于麦株由上向下数第3～4叶位上;在不同叶位上的虫量,多以叶片反面相对最多,其次为叶鞘和叶片正面。     

The Namibian Scoring System (NASS) version 2 rapid bio-assessment method for rivers

This paper presents a rapid bio-assessment method for assessing the ecological condition of streams and rivers in Namibia. The method uses the composition and abundance of aquatic invertebrates, which are identified in the field, mostly to family level. The method is based on the South African Scoring System version 5 (SASS5), which has been modified to account for additional tropical invertebrate taxa that occur in northern Namibia. The method was applied to the Zambezi River near Katima Mulilo and NASS results were found to fluctuate predictably with changes in water level. Training of Namibian personnel to apply the method, as part of the National Water Quality Monitoring Programme, is recommended.     

A survey of the year 2003 literature on applications of isothermal titration calorimetry

Over the last decade isothermal titration calorimetry (ITC) has developed from a specialist method which was largely restricted in its use to dedicated experts, to a major, commercially available tool in the arsenal directed at understanding molecular interactions. The number of those proficient in this field has multiplied dramatically, as has the range of experiments to which this method has been applied. This has led to an overwhelming amount of new data and novel applications to be assessed. With the increasing number of publications in this field comes a need to highlight works of interest and impact. In this overview of the literature we have attempted to draw attention to papers and issues for which both the experienced calorimetrist and the interested dilettante hopefully will share our enthusiasm.     

涡度相关观测的能量闭合状况及其对农田蒸散测定的影响

涡度相关法被认为是测定农田蒸散量的标准方法。然而,能量不闭合现象在涡度相关测量中普遍存在。分析能量不闭合对涡度相关观测的影响,对于提高涡度相关观测精度具有重要意义。以蒸渗仪法为参照,探讨涡度相关观测的能量闭合状况对农田蒸散测定的影响,在导致涡度相关观测能量不闭合的诸多因素中,寻找对蒸散测定有影响的因素。结果表明:涡度相关观测的白天能量平衡比率(EBR)呈秋冬高、春夏低的变化特征,麦季日均EBR范围在0.26—2.84之间,平均1.15;玉米季日均EBR范围在0.19—2.59之间,平均0.78。无论麦季或玉米季,涡度相关法测定的平均蒸散量(ETec)均明显低于蒸渗仪法观测值(ETL),但两者显著相关(P<0.01),并有相似的季节变化。平均蒸散比(ETec/ETL)麦季约为0.61,玉米季约为0.50。在冬小麦田和夏玉米田,ETec/ETL均与EBR显著相关(P<0.01)。麦田种植密度大,下垫面较均匀,蒸散比与EBR成正比(P<0.01),且不受叶面积指数(LAI)大小影响;反之,玉米田种植密度小,只有当LAI>1,下垫面变得较均匀后,蒸散比与EBR的关系才变得显著(P<0.01)。风速小时ETec/ETL与EBR显著相关,风速增加时二者相关性减弱。尤其在玉米田,当摩擦风速(u*)大于0.3 m/s时,ETec/ETL与EBR的相关性不再显著。风速小时,大气湍流微弱,湍流的涡旋较大。在有限的观测时段(0.5h)内,涡度相关仪的传感器难以捕捉足够的湍涡能量,所测湍流能量偏低,导致能量不闭合。以上结果为应用能量平衡比率校正农田蒸散提供了可能途径。     

Physical model of the plant tissue response to exposure to the microwave electromagnetic field

A hypothesis was suggested to explain the effect of biostimulation of seeds exposed to microwave electromagnetic field. It was shown that the assumption on the determining influence of the microwave field on the transport properties of the conducting system of a plant satisfactorily explains the phenomena observed in germinating seeds and growing plants. A physical model of the response of a plant cell to a microwave field is presented, which served as a basis for the method of calculating the maximum possible time of exposure of plant tissue.     

Faster, simpler, more-specific methods for improved molecular detection of Phytophthora ramorum in the field

Phytophthora ramorum is the causal agent of sudden oak death. The pathogen also affects a wide range of tree, shrub, and herbaceous species in natural and landscaped environments as well as plants in the nursery industry. A TaqMan real-time PCR method for the detection of this pathogen in the field has been described previously; this paper describes the development of a number of assays based on this method which have various advantages for use in the field. A scorpion real-time PCR assay that is twice as fast as TaqMan was developed, allowing the detection of P. ramorum in less than 30 min. Also designed was a loop-mediated isothermal amplification (LAMP) assay, which allowed sensitive and specific detection of P. ramorum in 45 min using only a heated block. A positive reaction was identified by the detection of the LAMP product by color change visible to the naked eye.     

A Continuum theory for the prediction of lateral and rotational positioning of α-helices in membrane proteins: Bacteriorhodopsin

We have developed a new method for the prediction of the lateral and the rotational positioning of transmembrane helices, based upon the present status of knowledge about the dominant interaction of the tertiary structure formation. The basic assumption about the interaction is that the interhelix binding is due to the polar interactions and that very short extramembrane loop segments restrict the relative position of the helices. Another assumption is made for the simplification of the prediction that a helix may be regarded as a continuum rod having polar interaction fields around it. The polar interaction field is calculated by a probe helix method, using a copolymer of serine and alanine as probe helices. The lateral position of helices is determined by the strength of the interhelix binding estimated from the polar interaction field together with the length of linking loop segments. The rotational positioning is determined by the polar interaction field, assuming the optimum lateral configuration. The structural change due to the binding of a prosthetic group is calculated, fixing the rotational freedom of a helix that is connected to the prosthetic group. Applying this method to bacteriorhodopsin, the optimum lateral and rotational positioning of transmembrane helices that are very similar to the experimental configuration was obtained. This method was implemented by a software system, which was developed for this work, and automatic calculation became possible for membrane proteins comprised of several transmembrane helices. © 1995 Wiley-Liss, Inc.     

In Vitro Multiplication of Phoenix dactylifera (L)

A method of microcloning via somatic embryogenesis was established in date palm (Phoenix dactylifera L) cultivars. The method has potential for commercial application. Embryogenic cultures were initiated from soft primordial tissues of 2-3-year-old female suckers. The system was optimized first for the genotype ’sayar’ and then its applicability was tested to other genotypes. A method of pre-acclimation using pre-acclimation chambers has been devised, which improved hardening survival greatly. More than 80 clones obtained from the genotype ’sayar’ have been shifted to field for agronomic evaluation.     

A model for the separation of large DNA molecules by crossed field gel electrophoresis.

The idea that large DNA molecules adopt a stretched conformation as they pass through gels suggests a simple mechanism for the separation of DNA by crossed field electrophoresis: at each change in field direction a DNA molecule takes off in the new direction of the field by a movement which is led by what was formerly its back end. The effect of this ratcheting motion is to subtract from the DNA molecule's forward movement, at each step, an amount which is proportional to its length. We find that this model explains most of the features of the separation, and we describe experiments, using a novel electrophoresis apparatus, which support the model. The apparatus turns the gel between two preset orientations in a uniform electric field at preset time intervals. This separation method has the practical advantage over some others that the DNA molecules follow straight tracks. A further advantage is that the parameters which determine the separation are readily predicted from the simple theory describing their motion.