Phosphorus detection in vitrified bacteria by cryo‐STEM annular dark‐field analysis

Bacterial cells often contain dense granules. Among these, polyphosphate bodies (PPBs) store inorganic phosphate for a variety of essential functions. Identification of PPBs has until now been accomplished by analytical methods that required drying or chemically fixing the cells. These methods entail large electron doses that are incompatible with low‐dose imaging of cryogenic specimens. We show here that Scanning Transmission Electron Microscopy (STEM) of fully hydrated, intact, vitrified bacteria provides a simple means for mapping of phosphorus‐containing dense granules based on quantitative sensitivity of the electron scattering to atomic number. A coarse resolution of the scattering angles distinguishes phosphorus from the abundant lighter atoms: carbon, nitrogen and oxygen. The theoretical basis is similar to Z contrast of materials science. EDX provides a positive identification of phosphorus, but importantly, the method need not involve a more severe electron dose than that required for imaging. The approach should prove useful in general for mapping of heavy elements in cryopreserved specimens when the element identity is known from the biological context.     

AUTOMATIC EXTRACTING AS AN INTERACTIVE PROCESS

In our study we have tried to evaluate most of the existing methods of automatic extracting and to combine them into one single system for text reduction. Hitherto, all existing automatic extracting systems have produced only extracts of documents: they select certain sentences from the full text and list them in text order.

Despite the result that statistical methods can be used for extracting German language texts (and that similar methods show best results for German and English texts) the main outcome of this study was that computer-based methods for text extracting can alter the whole extracting and abstracting process as such and lead to completely new and as yet unknown aspects of text reduction: the tailormade extract and extracting as an interactive process.     

COMPUTER AIDED DESIGN OF HORN RADIATORS FOR SATELLITE COMMUNICATION BY LEAST SQUARES OPTIMIZATION

Computer aided design optimization of corrugated horns became a powerful tool to reduce development costs on the one hand and to improve performance of space antennas on the other. In this paper the physical model is outlined, based on Maxwell's equations, and it is shown how a complete numerical simulation of a circular corrugated horn can be achieved, assuming that the interior geometry of the horn is known. In order to compute the electromagnetic properties of a horn, the so-called scattering matrix is assembled. This matrix is needed to relate mode amplitudes of reflected and transmitted waves in horn sections with different diameters. Envelope functions, determined by a few geometric design parameters, are used to describe the inner geometry of a horn. These parameters are applied to formulate a least squares optimization problem. As a starting point, an amplitude spectrum in the aperture has to be determined which radiates a given far field. The differences between those amplitudes and the amplitudes predicted by the model are to become as small as possible by adapting the design variables. Moreover, the return loss is to be minimized. The resulting least squares optimization problem can be solved by a standard sequential quadratic programming (SQP) code after a suitable transformation into a nonlinear programming problem, by which typical features of Gauss-Newton methods are retained. Some numerical results are included to show the successful application of the introduced advance to design a circular corrugated horn which radiates a given far field.     

A PHYSICO-CHEMICAL STUDY OF THE MECHANICAL PROPERTIES OF LOW AND INTERMEDIATE MOISTURE FOODS*

A number of textural properties of precooked, freeze-dried beef were examined by a cutting-extrusion test (force) and by a compression test (seven different properties). The tests were performed at different points of the moisture sorption isotherm over the complete range of water activity, A_w. In cutting-extrusion experiments (Allo Kramer Shear Press), a maximum in the force vs. A_w curve was observed at about A_w= 0.85. In compression experiments (Instron Universal Testing Apparatus), important changes of the textural properties were found in the range A_w= 0.15–0.30. These changes were paralleled by changes in the thermodynamic functions of water vapor sorption, especially in the standard differential entropy. Thermodynamic theory and mechanical measurements were used to interpret the textural changes in terms of increased crystallinity and subsequent swelling of the food structure.     

A simple and stable autofocusing protocol for long multidimensional live cell microscopy

Focus maintenance is a challenging problem in multidimensional wide‐field microscopy. Most automated microscopes use software algorithms, which are applied to z‐sections of the object, to select for the plane with the best signal to noise ratio. When applied automatically in multidimensional imaging applications, autofocus routines significantly increase light exposure and can become cytotoxic if applied too frequently. In addition, automated focusing procedures can readily focus on unwanted high contrast objects. By labelling a defined position with a fluorescent marker, we were able to separate the focusing procedure from the actual image acquisition positions and therefore overcome some of the major drawbacks of routine autofocus procedures. To implement this method in a multidimensional acquisition experiment, we created a visual basic‐based program, which is run prior to each image acquisition. This technique allows tight control of focus whilst keeping light toxicity in live cell imaging experiments to a minimum.     

DIFFUSION of LOW-MOLECULAR COMPOUNDS IN FOOD MODEL SYSTEMS

The diffusion of NaCl and isopropanol was studied in a matrix of pure gel and one containing either carbohydrates, proteins or fat using the concentration-distance method. Concentrations of NaCl were measured by conductivity, those of isopropanol by gas chromatography. Diffusion experiments have shown that the temperature dependence of the diffusion coefficient is in accordance with an Arrhenius approach.
Experimental and predicted diffusion coefficients didnot agree satisfactorily when only models of mere obstruction were considered. Including the effect of hydration by values obtained from pure gels, experimental diffusion coefficients range throughout between the calculated values of mere obstruction and those obtained from a mathematical combination of obstruction and maximum hydration.     

NMR Study of Adsorbate Self-Diffusion in Porous Glasses

The NMR pulsed field gradient technique was used to study molecular transport in porous glasses. The adsorbent materials were produced by leaching phase-separated sodium-boron-silica glasses of different composition, then heat-treating. The pore diameters of the glass samples produced were within the interval 0.8 to 50 nm. Water, methanol, dodecane, and do-decene were used as adsorbates. The coefficients of adsorbate self-diffusion were found to decrease with decreasing pore diameter. In comparison with the neat liquids, a reduction in the adsorbate mobility (up to two orders of magnitude) was observed. For the larger pores, that decrease may be attributed to the tortuosity of the adsorbent, whereas the low diffusivities in the porous glasses with small pores are a consequence of the stabilizing effect of the rigid adsorbent framework.     

Response of Shiraz grapevines to five different training systems in the Barossa Valley, Australia

Own‐rooted Shiraz, spaced 1.5 m apart in 2.75 m wide rows, were compared under five different training systems in the Barossa Valley, South Australia over five seasons starting 1995–96. Our objective was to determine how training affected fruit composition and crop yield in a context of efficient vineyard management. Training systems were: (i) low single wire (LSW), in which vines were trained to bi‐lateral cordons, 1.0 m above the ground, non‐shoot‐positioned; (ii) high single wire (HSW), a higher cordon (1.8 m) version of LSW; (iii) vertically shoot positioned (VSP); (iv) Scott Henry, where canopies of alternate vines were cordon‐trained and shoot‐positioned upwards (SHU) or downwards (SHD); and (v) minimally pruned (MIN), the same as LSW, except vines were not annually spur‐pruned. Crop yields (kg/m of row), over four seasons, averaged 4.9 (MIN), 2.9 (combined Scott Henry), 3.2 (VSP), 2.6 (HSW) and 2.9 (LSW). The greatest year‐to‐year variation in yield occurred with MIN and Scott Henry training. Crop weight of SHD vines was inferior to that of SHU vines in two seasons due to fewer shoots and bunches per vine, and to fewer bunches per shoot. Individual berry weights (g) were consistently least with MIN (0.89), and greatest with VSP (1.17). Fruit from all training systems exhibited similar rates of sugar accumulation during two seasons in which repeated measures of fruit maturation were made. Excepting the relatively light yields observed in 1999–2000, sugar accumulation was delayed in MIN vines, relative to other training systems, even when MIN harvest was delayed up to two weeks. The delay is most readily explained by the greater crops of MIN vines. Berry total anthocyanins and total phenolics concentrations (mg/g berry fresh wt.) at harvest were not greatly affected by training system. Berry anthocyanins and total phenolics exhibited a negative relationship with crop/m of canopy and a slight positive relationship with bunch exposure when evaluated across all training systems. Experimental plot soil depth and water availability affected cane pruning weights, yield per vine, berry weight, and canopy characteristics. LSW, HSW and MIN training systems all provided good yields of high quality fruit, although MIN did have a tendency to produce excessive crops in some years. VSP and Scott Henry training were less attractive due to their inherently greater canopy management requirements.