2,488 research outputs found
A machine vision system for automated non-invasive assessment of cell viability via dark field microscopy, wavelet feature selection and classification
Get PDFWei N, Flaschel E, Friehs K, Nattkemper TW. A machine vision system for automated non-invasive assessment of cell viability via dark field microscopy, wavelet feature selection and classification. BMC Bioinformatics. 2008;9(1):449.Background: Cell viability is one of the basic properties indicating the physiological state of the cell, thus, it has long been one of the major considerations in biotechnological applications. Conventional methods for extracting information about cell viability usually need reagents to be applied on the targeted cells. These reagent-based techniques are reliable and versatile, however, some of them might be invasive and even toxic to the target cells. In support of automated noninvasive assessment of cell viability, a machine vision system has been developed. Results: This system is based on supervised learning technique. It learns from images of certain kinds of cell populations and trains some classifiers. These trained classifiers are then employed to evaluate the images of given cell populations obtained via dark field microscopy. Wavelet decomposition is performed on the cell images. Energy and entropy are computed for each wavelet subimage as features. A feature selection algorithm is implemented to achieve better performance. Correlation between the results from the machine vision system and commonly accepted gold standards becomes stronger if wavelet features are utilized. The best performance is achieved with a selected subset of wavelet features. Conclusion: The machine vision system based on dark field microscopy in conjugation with supervised machine learning and wavelet feature selection automates the cell viability assessment, and yields comparable results to commonly accepted methods. Wavelet features are found to be suitable to describe the discriminative properties of the live and dead cells in viability classification. According to the analysis, live cells exhibit morphologically more details and are intracellularly more organized than dead ones, which display more homogeneous and diffuse gray values throughout the cells. Feature selection increases the system's performance. The reason lies in the fact that feature selection plays a role of excluding redundant or misleading information that may be contained in the raw data, and leads to better results
Substitution of Asp189 residue alters the activity and thermostability of Geobacillus sp NTU 03 lipase
No full textNadere verfijning DUROSTA-model: Toetsing H/Tw-parameter en aanpassing t.b.v. porositeitsverschillen en strandtransporten
No full textTeneinde het DUROSTA-model verder te verbeteren zijn de effecten modellering nader onderzocht en is de schaalgrootheid H/Tw nader bekeken.TAW/EN
A machine vision-based in situ probe for automated on-line measurement of cell density and viability by dark field microscopy, image processing and pattern recognition
Get PDFWei N. A machine vision-based in situ probe for automated on-line measurement of cell density and viability by dark field microscopy, image processing and pattern recognition. Bielefeld (Germany): Bielefeld University; 2007.The goal of this thesis is to develop an on-line probe that can be implemented to measure the in situ cell density and viability in bioreactors. This task includes not only hardware development, but also the development of suitable software that can fast and accurately process the signal generated by the hardware.
In spite of the diversity of the methods for on-line measuring cell density or viability separately, it appeared to be a nontrivial task to build a probe suitable for both properties. Even a simple combination of any two of the techniques would lead to great technical complexity. In order to avoid the system complexity, a special probe based on dark field microscopy has been proposed in this work. A reflective condenser has been designed and built to achieve dark field illumination and high contrast images. The imaging system of the probe is also designed and configured in accordance with the system's requirements.
In order to obtain accurate cell density and viability, programs have been written to evaluate the images captured by the probe. The core of the programs is implementing classifiers based on supervised machine learning. Different pattern recognition methods have been utilized in order to find the best way of image processing for the system
Route to 100 TW Ti: Sapphire laser at repetitive mode
No full textWe demonstrated a 100 TW-class femtosecond Ti: sapphire laser running at repetition rate of 0.1 Hz by adding a stage amplifier in the 20 TW/10 Hz laser facility (XL-II). Pumping the new stage amplifier with the 25 J green Nd:glass laser, we successfully upgraded the laser energy to 3.4 J with duration of 29 fs, corresponding to a peak power of 117 TW
Development of a rotor model for the numerical simulation of helicopter exterior flow-fields
No full textIncludes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena
Third body effects in the period changes of two Algol binaries: V342 Aql and TW Lac
Get PDF32nd International Physics Congress of Turkish-Physical-Society (TPS) -- SEP 06-09, 2016 -- Bodrum, TURKEYThe O - C diagrams of two Algol-type eclipsing binaries V342 Aql and TW Lac have been analyzed with the least-squares method by using all available minima times. The period changes in their O - C diagrams have been discussed with respect to the Light-Time Effect (LITE) that originates from gravitational influence of a third body. New LITE elements, orbital periods and possible minimum masses of third bodies are given.Turkish Phys So
Increasing science, technology, engineering, and mathematics skills using Project Lead the Way
Get PDFIncludes bibliographical references
High-efficiency supercontinuum generation in solid thin plates at 0.1 TW level
No full text
Supercontinuum generation in a solid-state medium was investigated experimentally. A continuum covering 460 to 950 nm was obtained when 0.8 mJ/30 fs Ti: sapphire laser pulses were applied to seven thin fused silica plates at a 1 kHz repetition rate. The primary processes responsible for spectral broadening were self-phase modulation (SPM) and self-steepening, while SPM and self-focusing were balanced to optimize the spectral broadening and suppress the multi-photon process. The output was compressed to a 5.4 fs and a 0.68 mJ pulse, corresponding to two optical cycles and 0.13 TW of peak power. (C) 2017 Optical Society of America</p
PROCESSED-BASED BUILDING CONSTRUCTION MANAGEMENT SYSTEM AND METHOD THEREOF
No full textI659368TWN1G06Q-010/06(2012.01)1061039912018302992018/08/162019/05/11一種以施工流程為基礎之建築施工流程管理系統，係包含:一設定模組，係包含一施工
流程管理介面，該施工流程管理介面用以根據施工流程建立複數個基本工作項目，並根 據一編碼規則進行編碼以提供一唯一工程編碼給各個該基本工作項目，使各個該基本工 作項目具有施工流程及該唯一工程編碼;一資料庫，係與該設定模組連接，並儲存該些 基本工作項目及其施工流程;以及一專案管理模組，係與該資料庫連接，並用以由該些 基本工作項目中選擇至少一部份以建立複數專案工作項目以形成一工程專案，使該工程 專案之該些專案工作項目對應於至少一部分的該些基本工作項目，藉此供一使用者能根 據該些專案工作項目之施工流程管理該工程專案。補正完
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