Real time small-angle X-ray scattering from polystyrene crazes during fatigue

Real time small-angle X-ray scattering (SAXS) from polystyrene (PS) crazed in cyclic three-point bending is investigated using intense X-ray radiation from the Cornell High Energy Synchrotron Source, CHESS. The SAXS patterns are recorded using a two-dimensional image intensifier/TV camera/video tape recorder system, operating at 30 frames/sec. At the maximum of the load cycle the SAXS pattern has a well defined streak normal to the craze fibrils. During the unloading portion of the cycle, however, the streak decreases in intensity and is spread into a diffuse fan. The loss of intensity is due to the decrease in volume of craze matter in the beam as the craze closes while the spreading of the diffraction pattern is due to the disorientation of the craze fibrils as they buckle in response to compression by the surrounding polymer matrix. Whilst reloading of the sample causes a relatively narrow SAXS streak to reappear, at the maximum load irreversible changes occur in the pattern from one cycle to the next. These changes are due to both an increase in craze fibril volume in the beam (craze growth) and to fibril breakdown and permanent disorientation.     

Colour image retrieval based on DCT-domain vector quantisation index histograms

A new kind of feature for colour image retrieval based on DCT-domain vector quantisation (VQ) index histograms (DCTVQIH) is proposed. For each colour image in the database, 12 histograms (four for each colour component) are calculated from 12 DCT-VQ index sequences, respectively. The retrieval simulation results show that, compared with the traditional spatial-domain colour-histogram-based features, the proposed features can largely improve the recall and precision performance.     

Productivity Through Automation

Productivity improvements in systems development can be made through the adoption of computer-aided software engineering (CASE), data design, and prototyping tools. How much these tools contribute to increased productivity in systems design, however, relies mostly on careful evaluation and selection of these tools as well as an evaluation of their impact on the designer or analyst who will be using the tool and on the development methodology itself.     

Budgets, Blood, and Turnips

Although the need for new systems (instead of constant maintenance of older systems) is often quite apparent to the MIS department, their advantages are not so readily realized by senior management -which sees only costs and risks instead of benefits. As a result, MIS managers must prove the costs and benefits of such projects. This column examines the difficulty of measuring the costs and benefits of four generations of systems -batch, online, DBMS based, and maintenance motivated - and explains why MIS managers should not only rewrite old systems but turn their attention toward the development of new and innovative systems.     

Comparison of plastic films with different optical properties for soil covering in horticulture: test under simulated environmental conditions

Covering the soil with plastic film is an important method to modify soil temperature and improve the conditions for plant growth. For the optimal use of films in horticulture, it is necessary to quantify this effect, which depends particularly on the optical properties of the film. Five films, used mainly for soil covering in asparagus cultivation, were tested by measuring the soil temperature as well as the transmittance and reflectance in the short‐ and long‐wavelength bands: ‘Taschenfolie schwarz/weiß’, a film with black and white surfaces and pockets for fastening; ‘Antitaufolie’, a film with anti‐condensation coating, ‘Solartherm plus Folie’, a film with black top and transparent sides; ‘MaterBi Folie’, a biodegradable film; and ‘Thermoplus Folie’, a black polyethylene with transparent sides. All films were produced in Germany. The temperature measurements were carried out under controlled irradiation (short‐wavelength band) and ambient temperature conditions in the laboratory: first, 182 W m^?2 and 11 °C at a depth of 0.4 m, and second, 340 W m^?2 at 20 °C. A significant relationship between the temperature increase or decrease by covering the soil with the film and the calculated apparent quantities of the reflectance in the short and long‐wavelength band was derived (r² = 0.85, n = 12). Furthermore, first tests with a physical model were carried out to obtain basic information, which should be used in the development of strategies for film management in the field. Copyright © 2004 Society of Chemical Industry     

Real-time cellular uptake of serotonin using fluorescence lifetime imaging with two-photon excitation

The real-time uptake of serotonin, a neurotransmitter, by rat leukemia mast cell line RBL-2H3 and 5-hydroxytryptophan by Chinese hamster V79 cells has been studied by fluorescence lifetime imaging microscopy (FLIM), monitoring ultraviolet (340 nm) fluorescence induced by two-photon subpicosecond 630 nm excitation. Comparison with two-photon excitation with 590 nm photons or by three-photon excitation at 740 nm shows that the use of 630 nm excitation provides optimal signal intensity and lowered background from auto-fluorescence of other cellular components. In intact cells, we observe using FLIM three distinct fluorescence lifetimes of serotonin and 5-hydroxytryptophan according to location. The normal fluorescence lifetimes of both serotonin (3.8 ns) and 5-hydroxytryptophan (3.5 ns) in solution are reduced to approximately 2.5 ns immediately on uptake into the cell cytosol. The lifetime of internalized serotonin in RBL-2H3 cells is further reduced to approximately 2.0 ns when stored within secretory vesicles.     

Presynaptic modulation of sensory neurons in the segmental ganglia of arthropods

The afferent terminals of arthropod sensory neurones receive abundant input synapses, usually closely intermingled with the sites of synaptic output. The majority of the input synapses use the neurotransmitter GABA, but in some afferents there is a significant glutamatergic or histaminergic component. GABA and histamine shunt afferent action potentials by increasing chloride conductance. Though glutamate can also have this effect in the arthropod central nervous system, its action on afferent terminals appears to be mediated by increases in potassium conductance or by the action of metabotropic receptors. The action of the presynaptic synapses on the afferents are many and varied. Even on the same afferent, they may have several distinct roles that can involve both tonic and phasic patterns of primary afferent depolarisation. Despite the ubiquity and importance of their effects however, the populations of neurones from which the presynaptic synapses are made, remain largely unidentified.     

Moving beyond ‘more crop per drop’: insights from two decades of research on agricultural water productivity

ABSTRACT

Concern over increasing water scarcity has led to the introduction of the concept of agricultural water productivity and an emphasis on interventions to achieve ‘more crop per drop’. Yet, a strong debate continues on how the concept is to be defined and used. Drawing largely from the irrigation literature, the origins of the concept and its methodological developments are reviewed, and its use in applied work over two decades is discussed. Based on this analysis of conceptual and applied research, key insights into the concept’s contributions and limitations are presented, as well as opportunities for further refinements.