Academic literature on the topic 'Small Particle Reagent'

Microfluidic devices or lab-on-a-chip systems can make a significant impact in many fields where obtaining a rapid response is critical, particularly in analyses involving biological cells. Microfluidics has revolutionized the manner in which many different assessments/processes are carried out, since it offers attractive advantages over traditional bench-scale techniques. Some of the advantages are: small sample and reagent amounts, higher resolution and sensitivity, improved level of integration and automation, lower cost and much shorter processing times. There is a growing interest on the development of techniques that can be used in microfluidics devices. Among these, electrokinetic techniques have shown great potential due to their flexibility. Dielectrophoresis (DEP) is an electrokinetic mechanism that refers to the interaction of a dielectric particle with a spatially non-uniform electric field; this leads to particle movement due to polarization effects. DEP offers great potential since it can be carried out employing DC and AC electric fields, and neutral and charged particles can be manipulated. This work is focused on the use of insulator based DEP (iDEP), a novel dielectrophoretic mode that employs arrays of insulating structures to generate dielectrophoretic forces. Successful microparticle manipulation can be achieved employing iDEP, due to its unique characteristics that allow for great flexibility. In this work, microchannels containing arrays of cylindrical insulating posts were employed to concentrate, sort and separate microparticles. Mathematical modeling with COMSOL® was performed to identify optimal device configuration. Different sets of experiments were carried out employing DC and AC potentials. The results demonstrated that effective and fast particle manipulation is possible by fine tuning dielectrophoretic force and electroosmotic flow.

One method of producing on-demand hydrogen for fuel cells is through the use of aluminum which reacts with water under certain conditions to produce hydrogen. This process can be used for applications as small as portable handheld devices, onboard generation for vehicles, or as large as a hydrogen refueling center. However, the utilization of aluminum for generating on-demand hydrogen is critically dependent on the control of the rate of hydrogen generation from the reaction. Experiments with micron and nano-sized aluminum powder are described in this work and the effects of particle size, reagent quantities, temperature and solution concentration on the hydrogen generation rate and total yield are analyzed and quantified. Regression models are developed and yield and rate predictions are confirmed. In general, aluminum nanoparticles are found to have poorer hydrogen yields, but marginally faster reaction rates as compared to micron particles.

The classic coagulation analyses based on the clot formation present basic disadvantages which make a standardization of reagents difficult. The use of photometry for coagulation methods represents nowadays an important step towards test optimization.We have evaluated a new analytical system (ChromoTimeSystem, Behringwerke AG, Marburg/FRG) based on a special instrument and reagents for photometric tests for coagulation and fibrinolysis. The instrument is a microprocessor-controlled 4-channel-photometer operating at 37°C and connected to a microcomputer. Photometric methods for prothrombin time (PT: Chromoquick®) and activated partial thromboplastin time (aPTT: Partochrom®) have been developed using a new chromogenic substrate (Tos-Gly-Pro-Arg-5-amino-2-nitro-benzoic-acid-isopropy-lamide) specific for thrombin. These tests are based on the time necessary to attain a fixed increase of absorbance (0.1 A). Tests for thrombin time (TT), batroxobin time and fibrinogen rely on turbidimetric techniques. In the screening tests PT, aPTT and fibrinogen 25 μl sample (TT: 50 μl) and 250 μl reagent are used. Single coagulation factors are assayed by mixing an undiluted sample (10 μl) with the correspondent factor deficient plasma (50 μl) in connection with the chromogenic PT or aPTT reagent (500 μl). The evaluated specific chromogenic substrate methods are: antithrombin III, α2-antiplasmin and plasminogen.Tne characteristics of the ChromoTimeSystem are: fibrinogen-independent PT and PTT, small sample volumes (10-50 μl), no predilution or preincubation, PT standardization according to WHO recommendations, coefficients of variation between 1 and 4 %, good correlation between photometric and coagulometric tests, the reference values for photom. PTT being 90-120 sec.

Discrete flow microfluidic devices have been identified as a technology that can be used to efficiently deliver health care services by reducing the cycle times and reagent consumption of common biological protocols and medical diagnostic procedures while reducing overhead costs by performing these applications at the point of care. Electrowetting on dielectric is one promising discrete flow microfluidic platform that can individually create, manipulate, and mix droplets through the application of asymmetric electric fields. The work presented outlines fundamental and practical contributions to the understanding and advancement of electrowetting on dielectric devices that the authors are using to develop a device capable of performing immunoassays on chip. Explicit analytical models for capillary force and the reduction in that force by contact angle hysteresis as a function of the three-dimensional shape of the droplet were derived to develop an empirically validated analytical model for transient motion of droplets in electrowetting on dielectric devices. This model accurately predicts the maximum droplet displacement and travel time to within 2.3% and 2.7%, respectively; whereas the average droplet velocity was always predicted to within 8.1%. It also demonstrates a method for real time monitoring of droplet composition, particle concentration, and chemical reactions in electrowetting on dielectric devices without optical access. This method has been used to determine the concentration of water-methanol solutions, measure the concentration of glass microspheres at various concentrations, and detect the chemical reactions that are typically used in immunoassays. A method for the mechanical filtration of droplets in these devices will also be presented. The proposed filtration method was successful at pore sizes at least two orders of magnitude below the droplet height, which is small enough to separate red and white blood cells in continuous flow microfluidic devices.

During the past years, there has been an increase in the number of power transformer failures worldwide linked by the presence of corrosive sulfur compounds in mineral insulating oil, leading to the formation of deposits of highly conductive copper sulfide or silver sulfide. In oils in operation, a highly reactive elemental sulfur, in a form of eight atom molecule of sulfur, S8, with a strong affinity for silver can be detected which present a significant threat to the contacts of the on load tap changer (OLTC). The high-temperature reactivation process of adsorbents during or after the regeneration process of mineral insulating oils leads to the contamination of insulating oil with elemental sulfur. The paper presents an innovative low-temperature process for the efficient removal of S8 from mineral insulating oil, based on the application of a small amount of iron particles coated with copper on its surface as a key component of the reagent mixture which is dispersed in polyethylene glycol. Intensive mixing of the reagent mixture with mineral insulating oil at temperatures below 100°C enables the complete removal of S8 from the oil. High process efficiency, the removal of S8 from the initial 15 mg/kg to levels below the detection limit, is achieved by using a small amount of the reagent mixture relative to the oil mass (<0.2 wt.%), in laboratory conditions and on a pilot scale experiments. Applying this process and subsequent treatment with adsorbents, insulating oils with improved physical, chemical and electrical characteristics are obtained, suitable for further use in power transformers. This procedure reduces potential environmental and economic risks associated with power transformer failures. The next phase will involve further process optimization and industrial plant implementation.

During the past years, there has been an increase in the number of power transformer failures worldwide linked by the presence of corrosive sulfur compounds in mineral insulating oil, leading to the formation of deposits of highly conductive copper sulfide or silver sulfide. In oils in operation, a highly reactive elemental sulfur, in a form of eight atom molecule of sulfur, S8, with a strong affinity for silver can be detected which present a significant threat to the contacts of the on load tap changer (OLTC). The high-temperature reactivation process of adsorbents during or after the regeneration process of mineral insulating oils leads to the contamination of insulating oil with elemental sulfur. The paper presents an innovative low-temperature process for the efficient removal of S8 from mineral insulating oil, based on the application of a small amount of iron particles coated with copper on its surface as a key component of the reagent mixture which is dispersed in polyethylene glycol. Intensive mixing of the reagent mixture with mineral insulating oil at temperatures below 100°C enables the complete removal of S8 from the oil. High process efficiency, the removal of S8 from the initial 15 mg/kg to levels below the detection limit, is achieved by using a small amount of the reagent mixture relative to the oil mass (<0.2 wt.%), in laboratory conditions and on a pilot scale experiments. Applying this process and subsequent treatment with adsorbents, insulating oils with improved physical, chemical and electrical characteristics are obtained, suitable for further use in power transformers. This procedure reduces potential environmental and economic risks associated with power transformer failures. The next phase will involve further process optimization and industrial plant implementation.

Microscale technologies are a powerful tool in many biological and chemical applications, as they utilize only small reagent volumes. Microfluidics is especially well compatible with biological materials and applications, for example protein crystallization, high throughput assay analysis, and various cell studies. In that context, non-linear gradients of particles and molecules as well as efficient mixing of the components inside the lab-on-a-chip are crucial for many experimental studies: testing of and analyzing biological responses to different analyte concentration levels, studying the native cell microenvironment or cellular responses during different growth and proliferation stages. Thus, a microfluidic approach that allows for generation of different concentration gradients and specifically exponential gradients emerges as a helpful technology, and is also compatible with cells.

The project under the acronym "GreenCleanS" aims to develop a new technology for removing elemental sulfur, in a form of eight atom molecule of suphur, S8, from mineral insulating oils. Under the acronym GreenCleanS, a unique technology is being developed based on low-temperature eco-friendly treatment, which does not emit pollution while efficiently removing elemental sulfur from mineral insulating oils, unlike existing technologies worldwide which can be pollutant emitters (if polychlorinated biphenyls are present in the oil), do not remove elemental sulfur, and, moreover create it as a by-product of the reactivation procedures of the adsorbents used. The development of this technology for removing elemental sulfur from transformer oils will involve treatments of insulating oil under laboratory conditions and at a pilot scale experiments, followed by a demonstration of the developed technology in operational environments on-site at the mobile facility of the Nikola Tesla Institute. The procedure is based on the application of a small amount of iron particles coated with copper on its surface as a key component of the reagent mixture which is dispersed in polyethylene glycol. Intensive mixing of the reagent mixture with mineral insulating oil at temperatures below 100°C enables the complete removal of S8 from the oil. High process efficiency, the removal of S8 from the initial 15 mg/kg to levels below the detection limit, is achieved by using a small amount of the reagent mixture relative to the oil mass (<0.2 wt.%), in laboratory conditions and on a pilot scale experiments. Applying this process and subsequent treatment with adsorbents, insulating oils with improved physical, chemical and electrical characteristics are obtained, suitable for further use in power transformers. Integration of the GreenCleanS desulfurization procedure with a previously developed and patented technology for removing polychlorinated biphenyls and corrosive dibenzyl disulfide will create a unique multifunctional technology enabling simultaneous removal of all unwanted compounds from mineral insulating oils. This technology represents a significant advancement over existing procedures that can be pollutants or inefficient in removing elemental sulfur, providing an extremely efficient solution with minimal environmental impact.

Lab-on-a-chip devices are miniaturized bio-medical laboratories on a small glass/plastic plate. These lab chips can duplicate the specialized functions of their room-sized counterparts such as clinical diagnoses and tests. The key microfluidic functions required in various lab-on-a-chip devices include pumping and mixing liquids, controlling bio-reactions, dispensing samples and reagents, and separating molecules and cells/particles. Using electrokinetic microfluidics to realize these functions can make the devices fully automatic, independent of external support (e.g., tubing, valves and pump), and truly portable. Understanding, modeling and controlling of various electrokinetic microfluidic phenomena and the electrokinetic microfluidic processes are essential to systematic design and operation control of the lab-on-a-chip systems. This presentation will explain the principles of these electrokinetic microfluidic processes and how they are used in lab-on-a-chip devices. Some lab-on-a-chip devices such as real-time PCR chip, immunoassay chip and flow cytometer chip developed in Dr. Li’s lab will be introduced.

The original objectives of this research project were to: (1) develop immunoassays, photometric sensors, and electrochemical sensors for real-time measurement of progesterone and estradiol in milk, (2) develop biosensors for measurement of caseins in milk, and (3) integrate and adapt these sensor technologies to create an automated electronic sensing system for operation in dairy parlors during milking. The overall direction of research was not changed, although the work was expanded to include other milk components such as urea and lactose. A second generation biosensor for on-line measurement of bovine progesterone was designed and tested. Anti-progesterone antibody was coated on small disks of nitrocellulose membrane, which were inserted in the reaction chamber prior to testing, and a real-time assay was developed. The biosensor was designed using micropumps and valves under computer control, and assayed fluid volumes on the order of 1 ml. An automated sampler was designed to draw a test volume of milk from the long milk tube using a 4-way pinch valve. The system could execute a measurement cycle in about 10 min. Progesterone could be measured at concentrations low enough to distinguish luteal-phase from follicular-phase cows. The potential of the sensor to detect actual ovulatory events was compared with standard methods of estrus detection, including human observation and an activity monitor. The biosensor correctly identified all ovulatory events during its testperiod, but the variability at low progesterone concentrations triggered some false positives. Direct on-line measurement and intelligent interpretation of reproductive hormone profiles offers the potential for substantial improvement in reproductive management. A simple potentiometric method for measurement of milk protein was developed and tested. The method was based on the fact that proteins bind iodine. When proteins are added to a solution of the redox couple iodine/iodide (I-I2), the concentration of free iodine is changed and, as a consequence, the potential between two electrodes immersed in the solution is changed. The method worked well with analytical casein solutions and accurately measured concentrations of analytical caseins added to fresh milk. When tested with actual milk samples, the correlation between the sensor readings and the reference lab results (of both total proteins and casein content) was inferior to that of analytical casein. A number of different technologies were explored for the analysis of milk urea, and a manometric technique was selected for the final design. In the new sensor, urea in the sample was hydrolyzed to ammonium and carbonate by the enzyme urease, and subsequent shaking of the sample with citric acid in a sealed cell allowed urea to be estimated as a change in partial pressure of carbon dioxide. The pressure change in the cell was measured with a miniature piezoresistive pressure sensor, and effects of background dissolved gases and vapor pressures were corrected for by repeating the measurement of pressure developed in the sample without the addition of urease. Results were accurate in the physiological range of milk, the assay was faster than the typical milking period, and no toxic reagents were required. A sampling device was designed and built to passively draw milk from the long milk tube in the parlor. An electrochemical sensor for lactose was developed starting with a three-cascaded-enzyme sensor, evolving into two enzymes and CO2[Fe (CN)6] as a mediator, and then into a microflow injection system using poly-osmium modified screen-printed electrodes. The sensor was designed to serve multiple milking positions, using a manifold valve, a sampling valve, and two pumps. Disposable screen-printed electrodes with enzymatic membranes were used. The sensor was optimized for electrode coating components, flow rate, pH, and sample size, and the results correlated well (r2= 0.967) with known lactose concentrations.