Fitting the linear-quadratic model using time of occurrence as the end-point for quantal response multifraction experiments

A statistical technique is given for fitting the linear-quadratic model to experimental quantal response multifraction data using the time of the response as the end-point. The analysis used is based on the Cox Proportional Hazards model. The technique is useful for late effects where the time of occurrence of the response is dose dependent. The technique is compared to logistic regression analysis and the advantages and disadvantages are discussed. Both methods are applied to a lung pneumonitis experiment and a kidney experiment.     

微生物生态学研究方法进展

微生物培养及显微技术作为鉴定微生物种群的手段有很大的局限性,因为环境中大多数微生物处于“存活但不能培养”的状态。因此．不依赖于微生物培养的生物化学以及分子生物学方法正被广泛地用于微生物生态学研究。主要介绍了荧光技术。基于PCR的分析技术和PLFA等技术在表征微生物多样性研究中的某些进展。     

A comparison of heavy liquid floatation and microwave digestion techniques for the extraction of fossil phytoliths from sediments

This paper reports the results of a comparative analysis of two techniques used for the extraction of fossil phytoliths from sediments. The first is a standard heavy liquid floatation extraction technique that has been successfully used and proven to provide reliable phytolith assemblage data. A second technique using a Perkin-Elmer Multiwave Microwave Sample Preparation System is introduced, and the results are compared to those of the conventional technique. Results for both techniques, as well as the advantages and disadvantages of their use are discussed. This study provides an introduction to an alternative technique for the extraction of fossil phytoliths and possibly starch grains from sediments. The microwave technique is fast, inexpensive, omits the need for heavy liquid floatation and most importantly results in the appropriation of interpretable and replicable fossil phytolith assemblage data.     

Measurement of pulsatile flows and variable volumes by bolus injection of indicator in a model of the pulmonary circulation

The reliability and accuracy of the bolus injection-dye dilution technique were assessed for a physiological range of frequencies (13-49 min-1) and stroke volumes (60-160 ml) on a glass model where flows and volumes varied as a preset function of time (n = 320). We found that the technique overestimates flow by about 8% with a 95% confidence interval of +/- 10% for one measurement. Mean transit times are accurate within a +/- 7% confidence interval for one measurement. In a time-dependent flow and volume system this technique measures the mean volume as related to time with fluctuations up to +/- 30% around the mean. Results are independent of time and site of injection. The double injection-single sampling technique gives results that are equivalent to those obtained by single injection and sampling of dye.     

The measurement of shear modulus and membrane surface viscosity of RBC membrane with Ektacytometry: a new technique

A new technique is proposed to estimate the shear modulus (mu) and membrane surface viscosity (eta(m)) of red blood cell (RBC). Theoretical formulae for finding these two parameters are first derived based on the force balance on a RBC in a flow field of low viscosity. Different types of Ektacytometry are then used to measure relevant quantities. The obtained values (mu=6.1 x 10(-6)N/m, eta(m)=8.8 x10 (-7)Ns/m for normal RBC) are consistent with those previously found by micropipette technique and in AC electric field. The present technique is, however, much easier to operate and more advantageous in reflecting the average properties of a large quantity of RBCs, and it is much cheaper to be applied in clinical practice than any other method of measuring the two parameters. The sensitivity of the technique is demonstrated by testing RBCs treated with glutaraldehyde of different concentrations. This technique was demonstrated by the flow chamber.     

X-射线CT扫描技术在中新世松属球果化石研究中的应用

利用X-射线CT扫描技术观察云南晚中新世松属球果化石的内部结构,并与现代种的内部结构进行比较。这是该技术在中国古植物学研究中的首次报道。通过内部结构的比较发现,松属化石最接近于现生种喀西亚松(Pinus kesiya)。CT扫描技术可以在不破坏标本的前提下观察植物化石的内部结构,对于较珍贵的化石研究作用尤为明显,但是分辨率的高低是该技术广泛应用于古植物学的重要因素,随着扫描仪器分辨率的不断提高,CT扫描技术将提供植物化石内部结构的更多细节信息,从而为古植物学研究开辟一条新的技术途径。     

An evaluation of techniques for measuring yield turgor in excised Salix leaves

Abstract. The use of three techniques for determining yield turgor in excised Salix leaves was investigated. These were the osmotic-solutions technique, the psychrometer technique, and the pressure-chamber technique. The application of the osmotic-solutions technique to a range of leaf types was discussed and the appropriate corrections for volume changes and the contribution of apoplastic water were detailed. It was concluded that the osmotic-solutions technique is not satisfactory for use with slowly growing and/or very elastic leaves. The psychrometer and pressure-chamber techniques were both simple compared with the osmotic-solutions technique, and gave values for yield turgor in the range of 0·3–0·5 MPa. A disadvantage of the psychrometer technique for field applications is that it requires one psychrometer chamber per sample. The pressure-chamber technique was modified for use as a field technique where multiple sampling could be easily and inexpensively achieved. Particular care was required with this technique to prevent water loss from the leaf during stress relaxation, but simple and effective procedures for doing so were found. The modified pressure-chamber technique described here, is recommended as the preferred technique for measuring the yield turgor of leaves in experiments where many simultaneous estimates of yield turgor are to be made.     

Fusion of plant protoplasts by electric fields

The electrical fusion technique of Zimmermann and Scheurich (1981 Planta 151: 26-32) has been used to fuse mesophyll protoplasts of Avena, Zea, Vigna, Petunia, and Amaranthus. Electrical fusion proves to be a simple, effective, and general fusion technique that can be controlled to form either dikaryons or large multinucleate fusion bodies. In addition, we show that Vigna mesophyll protoplasts that are subjected to the electrical fields used in this technique are viable in culture. The construction of the fusion chambers, necessary electrical equipment, and the fusion protocol are described in sufficient detail for reproduction of the technique.     

A continuous wave technique for the measurement of the elastic properties of cortical bone

A continuous wave technique is described for measuring the nine independent orthotropic elastic coefficients from a single cubic specimen. The side dimensions of this cubic specimen are on the order of 5 mm. Because of the small size of the specimen, the spatial resolution of material inhomogeneity using this technique is quite good. Although it is possible to apply this technique to any elastic material such as woods or metals, the elastic properties of human and canine cortical femora are presented here. The orthotropic elastic coefficients and the variation of these coefficients are presented as a function of anatomical position.     

A new change-in-ratio procedure robust to unequal catchability of types of animal

The change-in-ratio technique is a useful practical procedure for the estimation of game animal population sizes. The major problem with this technique is failure of the assumption that both types of animals are captured or sighted with equal probabilities. Here we extend the change-in-ratio technique to the case where there are two removals with emphasis on the special situation where there are two consecutive single-type removals. The advantage of this extension is that it allows an estimation procedure which is robust to unequal capture or sighting probabilities. It is also possible to test the assumption of equal sighting probabilities. Some numerical results on mean squared error of the population size estimator for the new design and the traditional design are given. The procedure is illustrated on some juvenile grass carp data collected in a small pond where the population size is known. We believe this technique is potentially useful to wildlife and fisheries biologists and that more statistical research would be beneficial.     

Comparative investigation of the mixed aggregation immunocytochemical technique and the indirect peroxidase technique for the detection of prostate specific acid phosphatase in paraffin or paraplast sections

Summary The results obtained with the indirect peroxidase technique for the identification of prostate specific acid phosphatase in formalin fixed, paraffin or paraplast embedded autopsy material are compared with the results obtained with the mixed aggregation immuno-cytochemical technique. When using a monospecific antiserum the former technique is prefered. However, when a monospecific antiserum is not available, one has to balance the advantages of the mixed aggregation immuno-cytochemical technique against the disadvantages of having to prepare a monospecific antiserum, necessary for the indirect peroxidase technique. Both methods appeared positive in 20 prostatic carcinomas and in 36 metastases of prostatic carcinomas. In the epithelium of the seminal vesicles and in osteoclasts no acid phosphatase could be detected with the antiserum. A comparison of both techniques, as well as different types of preincubation to diminish nonspecific background staining are discussed.     

Development of sludge filterability test to assess the solids removal potential of a sludge bed

A qualitative sludge characterisation technique called "sludge filterability technique" has been developed. This technique enables the determination of the sludge potential for the physical removal of solids, weighing the effect of different process parameters on solids removal and identifying the mechanisms of solids removal in an upflow anaerobic sludge bed system. In this paper guidelines for conducting the test are given and a "standardised" set-up is presented. The experimental set-up and protocol are simple and the results can be obtained in a period as short as a few hours. A sludge sample is added to an upflow reactor incubated at 4 degrees C, to limit gas production, washed with an anaerobically pre-treated and suspended solids free wastewater to remove solids washed out from the sludge, and then fed with a model substrate, prepared from fish meal with a standard procedure. Several experimental runs were conducted to validate and optimise the technique. The results showed that the technique is reliable, workable and reproducible.     

Development of a noninvasive technique for the measurement of intracranial pressure.

Intracranial pressure (ICP) dynamics are important for understanding adjustments to altered gravity. Previous flight observations document significant facial edema during exposure to microgravity, which suggests that ICP is elevated during microgravity. However, there are no experimental results obtained during space flight, primarily due to the invasiveness of currently available techniques. We have developed and refined a noninvasive technique to measure intracranial pressure noninvasively. The technique is based upon detecting skull movements of a few micrometers in association with altered intracranial pressure. We reported that the PPLL technique has enough sensitivity to detect changes in cranial distance associated with the pulsation of ICP in cadavera. In normal operations, however, we place a transducer on the scalp. Thus, we cannot rule out the possibility that the PPLL technique picks up cutaneous pulsation. The purpose of the present study was therefore to show that the PPLL technique has enough sensitivity to detect changes in cranial distance associated with cardiac cycles in vivo.     

Modified differential display technique that eliminates radioactivity and decreases screening time

Several techniques are available that detect variations in gene expression between cellular populations. These include subtractive hybridization (SH), differential colony hybridization (DCH) and mRNA differential display, all based on the analysis of mRNA. The first two techniques, however, are limited because they require large amounts of mRNA for SH or several rounds of screening for DCH. Differential display overcomes both of these limitations. However, the conventional differential display technique is plagued by false positives and is labor intensive. The identification of genes that are truly differentially expressed, therefore, becomes a formidable task. We describe a modified differential display technique that overcomes the limitations of the conventional technique. This new technique eliminates a source of false positives, decreases the time required to screen a set of primers and reduces the use of radioactivity.     

Comparative investigation of the mixed aggregation immunocytochemical technique and the indirect peroxidase technique for the detection of prostate specific acid phosphatase in paraffin or paraplast sections.

The results obtained with the indirect peroxidase technique for the identification of prostate specific acid phosphatase in formalin fixed, paraffin or paraplast embedded autopsy material are compared with the results obtained with the mixed aggregation immuno-cytochemical technique. When using a monospecific antiserum the former technique is prefered. However, when a monospecific antiserum is not available, one has to balance the advantages of the mixed aggregation immuno-cytochemical technique against the disadvantages of having to prepare a monospecific antiserum, necessary for the indirect peroxidase technique. Both methods appeared positive in 20 prostatic carcinomas and in 36 metastases of prostatic carcinomas. In the epithelium of the seminal vesicles and in osteoclasts no acid phosphatase could be detected with the antiserum. A comparison of both techniques, as well as different types of preincubation to diminish nonspecific background staining are discussed.     

Peak locater for multicomponent spectra

A sliding pivot technique capable of locating component peak maxima of multicomponent spectra is presented. The locations of peak maxima obtained in this way are shown to be the same as those of the minima in the second derivative. A major advantage over the second-derivative test is simply that derivative spectra are not needed. The sliding pivot technique requires only the original spectrum to locate the component peak maxima and consequently reduces the noise enhancement factor. The deconvoluted Fourier transform infrared spectrum of purple membrane is analyzed and compared to a Gaussian analysis and a second-derivative analysis. The sliding pivot technique identifies a band missed by second-derivative analysis.     

An examination of the soil washing technique by its application to several soils

Summary The soil-washing technique is discussed in relation to its efficiency in removing fungal spores from soil samples and to its application for studying soil microhabitats. Detailed data on the application of the technique to a range of soils are given, and an attempt is made to evaluate the potentialities of the technique for studies on soil fungi.     

Application of wound closure Molndal technique after laparoscopic cholecystectomy--initial comparative study

Because of a possible delayed wound healing, critical colonization and infection of wounds present a problem for surgeons. Colonized and infected wounds are a potential source for cross-infection. Molndal technique of wound dressing has proven to be effective in prevention of infection. Also the wound heal better and faster. In our study we wanted to describe the benefits of the Molndal technique wound dressing after laparoscopic cholecistectomy compared to traditional wound dressing technique. Molndal technique consisted of wound dressing with Aquacel Ag--Hydrofiber (ConvaTec, Dublin, Ireland). Traditional technique was performed using gauze compresses and hypoallergic adhesives. We analyzed the results of 100 patients after laparoscopic cholecystectomy. 50 patients were treated by Molndal technique and 50 patients by the traditional technique of wound dressing. In the group treated by Molndal technique only 1 (2%) patient has revealed a wound infection, proven by positive microbiological examination and suppuration, mostly in the subumbilical incision. In the traditional technique group 7 (14%) patients developed wound infection also predominantly in the subumbilical incision. The difference was statistically significant (p < 0.01). Our results are clearly showing that Molndal technique is effective in preventing the infection of subumbilical incision wound and is to by recommend for regular use at designated site after laparoscopic cholecistectomy.     

Description and validation of a non-invasive technique to measure the posture of all hand segments

The aim of this work is to describe and validate a technique for measuring the posture of all the segments of the hand in a non-invasive way. The technique uses digital photographic images to reconstruct 3-D location of markers drawn on the skin. The markers are defined to obtain joint rotation angles with physiological meaning. Different experiments have been developed in order to analyze the accuracy and repeatability of the angle measurements. Although the placement of markers does not require any special care, the errors due to their location are lower than 2.6 deg in all cases, thus assuring the repeatability of the technique.     

Direct measurement of dissolved gases in microbiological systems using membrane inlet mass spectrometry

Membrane inlet mass spectrometry is a novel technique that has been used to measure concentrations of dissolved gases and volatile compounds of microbiological interest. This technique is compared with other methods of measuring dissolved gases. Applications to some microbiological processes (respiration, photosynthesis, fermentation, nitrogen fixation and methanogenesis) are discussed in greater detail. The advantages of the technique and possible future developments are presented; its major attraction is that a number of different gases can be simultaneously and continuously monitored directly and non-invasively in cell suspensions.