148 research outputs found
A system to provide control of stimulation and acquisition of ionic currents in cell membranes [In: Proceedings of the physiological society p. 7]
No full textA program has been developed which controls the electrical stimulation of cell membranes with concurrent acquisition of the induced ionic currents. The software is written for a Cambridge Electronic Design (CED) type 1401 Intelligent LaboratoryInterface driven by a Sperry model 45 personal computer, which is highly compatible with the IBM XT.The CED 1401 is a sophisticated and flexible instrument that contains its own 6502 microprocessor and directly addressable 64 K memory, with up to 2 Mbytes of extra memory. Our software requires at least 0-25 Mbytes of this extra memory and uses (1) the digital-to-analogue (12-bit) capability to produce stimulus wave forms of programmable shape, (2) the analogue-to-digital converters (12 bit) to sample theevoked responses and (3) the internal 1401 clocks to control the timing of this stimulation and acquisition, and also to provide synchronization with other experimental apparatus. These features and others may all be used concurrently.The program is menu-driven; keyboard input is subject to extensive error trapping and run-time interaction with the system is achieved by use of function keys. A 'spreadsheet' format is used to input the variables defining the stimulus wave forms which can be stored on disk for subsequent use. Interactive control menus available during the experiment permit rapid retrieval of these sets of variables to suit current- or voltage-clamp experiments or to generate repetitive pulses which, for example,may be used to test for seal formation between a patch electrode and the cell membrane.A comprehensive range of sampling frequencies, up to 32 K conversions/s, are selectable. 'Windows' of 512-2048 points may be used to store selected portions of the evoked responses for subsequent display and analysis. Data with experimental details may also be stored on disk.The system was designed, developed and documented using the Jackson system of program development (Jackson, 1975; Giddings, 1984) and uses Pascal as thehigh-level language. This approach permits the program to be modified to meet the needs of the experimenter while maintaining a strict regime of modular program development
Electrohydrodynamic Atomization in the Simple-Jet Mode: Out-scaling and Application
No full textElectrohydrodynamic Atomization, often called electrospraying, is a way to disintegrate a liquid into droplets by exposing it to a strong electric field. Although William Gilbert has reported about the deformation of a liquid meniscus under the influence of an electric field already more than four centuries ago, the interest about electrostatic spraying of a liquid increased just a few decades from now. Among other advantages these systems can create droplets much smaller than the nozzle diameter with a narrow size distribution. The droplets are also electrically charged and can be manipulated to collide with specific surfaces (electrostatic coating) or with oppositely charged particles (bipolar coagulation). For a given liquid and setup, different combinations of the electric potential and flow rate can create different spraying modes. The ost studied mode is the cone-jet mode due to its capability to roduce droplets smaller than the nozzle diameter with a narrow size distribution. The characteristics and particularities of the different modes have been extensively studied and can be found in the literature. In this thesis we have explored another mode, the simple-jet mode. Compared to the cone-jet mode the simple-jet mode is much less explored. A possible reason for that is the fact that the droplet size in the latter is many times bigger than in the former mode for the same nozzle diameter. Nevertheless, because this mode operates at flow rates much higher than the cone-jet mode it is an interesting option for atomization methods which require high throughputs, e.g. water treatment and agricultural processes. We have studied the characteristics of this mode to resent its operational window and how the application of an electric field changes the droplet size and influences the droplets dispersion. Additionally we designed a multinozzle device for electrospraying in the simple-jet mode. We show that the device proposed can operate in this mode and that the characteristics of each individual nozzle are similar regarding flow per nozzle and produced droplet diameter. An insulation layer was applied between the nozzle tip and the counter electrode to allow its operation under high humidity levels without current leakages. The proposed configuration works for the simple-jet mode (the mode which presents the highest flow rate per nozzle in EHDA), therefore it offers very high throughput with a low number of nozzles per unit area. By coupling the device to a single step evaporator we have shown that the application of an electric potential increase the evaporation of the electrosprayed droplets inside a closed chamber by 40%. Lastly, we showed that positive electrosprays in the intermittent cone-jet mode can produce negatively charged droplets and explained their origin. The presented research evidences the necessity of exploring other electrohydrodynamic atomization modes (besides the cone-jet mode) and shows that the simple-jet mode might be a good option for systems which require a relatively high throughput. It also demonstrates that electrohydrodynamic atomization might be a good atomization method for systems like thermal desalination and other distillation processes.DelftChemTechApplied Science
Stock-taking of models existing for fibre transport and deposition in lungs and other tubelike systems
No full textFrom this literature search one may conclude that most authors write their article on the basis of an already existing paper: they publish a so called secondary model. The authors either make some adjusments to improve an existing model or test an existing model by doing experiments. It does not often occur that they do both modelling and experimental work.Applied SciencesMaterials ScienceParticle Technology Grou
The Golgi: A transition point in membrane lipid composition and topology
No full textThe exciting developments in the fields of sphingolipid-mediated signal transduction and sphingolipid-mediated protein sorting have led to a tremendous activity in the studies of sphingolipid organization in biomembranes, especially the structural role of sphingolipids in membrane rafts. It is now being realized that rafts may exist in many cellular membranes and that thus their functions are not limited to the plasma membrane. In order to fully grasp raft function, it will be necessary to identify and characterize the different types of raft, to follow their fate in time and to understand the role of the various sphingolipids in their structure.Applied Science
Multiangle multiscale characterization of seismic reflection data
No full textCivil Engineering and Geoscience
Optical determination of thermophoretic velocity
No full textThis graduation work describes the design and implementation of an apparatus for direct measurement of thermophoretic velocity. For particles larger than the mean free path of the suspension gas, there are two theories concerning this velocity, presented by Brock (1962) and Derjaguin and Yalamov (1965). To be able to develop promising future applications, especially in the field of micro-chip manufacture, there is a need for experimental data that can determine which theory is the correct one. The experimental setup used in this work is based on the detection of scattered light from moving particles. Particles are injected in a Millikan cell, where a controlled temperature gradient is present. The scattered light from a laser is magnified and detected by a CCD-camera. Images of moving particles are recorded on videotape. The velocity of an individual particle is determined by cross-correlation of time-separated images. The design of the optics is discussed extensively as well as a modification of the Millikan cell, necessary because of convection flows in the original cell. The cross-correlation is made with a computer programme especially designed for this experiment. It enables measurements of many individual velocities from a single experiment. The evaluation procedure is discussed thoroughly, both theoretical and practical. Measurements of settling velocities have shown that the experimental procedure can distinguish between particles, with a size difference less than 1 gm. Thermophoretic velocities have been determined for sodium chloride, titanium dioxide and PSL spheres at different temperature gradients. The results are compared to theoretical values. The size distribution of the aerosol is shown to have a large effect on the results in these experiments. The preliminary results indicate the superiority of the Brock theory
The improvement and upscaling of a laser assisted chemical vapor pyrolysis reactor
No full textChemE / NSMApplied Science
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