pH effects accompanying serological reactions

Thesis (M.A.)--Boston UniversityContributions of a number of scientists to the study of the operating forces in serological reactions led to the theory that at least some ionized groups must be involved in the specific combination of the antibody and antigen molecules. This theory, summarized by Pauling et al. (60), states that the affinity for specific antibody-antigen union depends on ordinary " short range" forces. One of these forces, Coulomb attraction, operates between oppositely charged ionized groups arranged in complementary pattern on the molecules with the serological properties. The advancement of ionized groups participation theory raised the question of whether there is a change in hydrogen ion concentration following the serological reactions. Hirsh (40) and later Smith ana Marrack (71) tried to solve the problem by determining the pH in diphtheria toxoid and its anti toxin reactions. Whereas Hirsh found great changes in pH during the serological reactions, Smith and Marrack reported that they could not find any pH change. In an effort to add some clarification to this problem this work was designed to determine the pH following the reactions of two serological systems: 1. Plant hemagglutinin (lectin) plus blood group A substance. 2. Diphtheria toxoid plus diphtheria antitoxin. Those systems were preferentially selected because the high percentage of lectins and diphtheria antitoxin are specifically precipitable with their corresponding antigens. Therefore they contain less inactive proteins to obscure any pH changes which may result from the union of antigen and antibody. The solutions of lectins and A substance were obtained from Dr. W. C. Boyd's laboratory at Boston University School of Medicine. The procedure of preparation is described by Boyd et al. (14). The A substance was prepared from commercial hog gastric mucin, essentially by the 90% phenol method of Morgan (1). Th e diphtheria toxoid and antitoxin were obtained from the Vaccine Department of Massachusetts Public Health Biologic Laboratories, and were prepared essentially by the methods of Banzhaf (3) and Mueller (54). The following an analytical data of those substances were reported by the suppliers: 1. Lectin, 40% concentr. in saline soln., 1.68 mg N/ml, 32-36% specifically precipitable antigens and antibodies 2. A substance, 1% concentr. in saline soln., 33% specifically precipitable antigens and antibodies 3. Diptheria antitoxin, 4200 Standard Units concentration, 6.48 mg N/ml, 29% (calculated) specifically precipitable antigens and antibodies 4. Diptheria toxoid, 4200 Lf Units concentration, 1.85 mg N/ml The pH's of the above solutions were measured, then the antibodies were mixed with their corresponding antigens by equal volumes and the pH's of the reacting mixtures were determined: a. Right after mixing b. 15 minutes after mixing c. 24 hours (refrigerated) after mixing. Using the weak solutions of HCl and HaOH the solutions of lectin and A substance were adjusted to the following pH's: 3.00; 3.70; 4.50; 7.00. By the same method the solutions of diphtheria toxoid end antitoxin were brought to the pH's: 4.00; 4.80; 5.83; 6.70; 7.50. Then equal volumes of the solutions of lectin and A substance were mixed together end the hydrogen ion concentration of the mixture was determined: a. Right after mixing b. 15 minutes after mixing c. 24 hours after mixing (refrigerated). Employing the same technique the solutions of diphtheria toxoid and antitoxin were combined by equal volumes and the pH readings were taken. In order to obtain some information about the buffer capacity of lectin, diphtheria antitoxin and A substance, 25 ml of each of those solutions was titrated with 0.1 N HCl and NaOH, and pH readings were taken after the addition of every 0.5 ml of acid or base. The instrument used fur pH determination was Cambridge Instrument Company pH meter No. 0-181356. The efficiency of the apparatus was found to be 0.03 pH units. The glassware used was dry and free of contamination. In the case of toxoid and antitoxin, the sterility was preserved throughout the work. RESULTS In a series of measurements performed at a wide range of pydrogen ion concentration of the reactants, no pH change was found in those serological reactions. The pH of combined solutions of lectin and A substance, as well as diphtheria toxoid and antitoxin, remained the same as the pH of those solutions before mixing. At pH 3.00 combined lectih and A substance solutions showed no sign of reaction; even 24 hours later no precipitate appeared in the test tube. The rest of the solutions, when combined at their corresponding pH, showed normal preciptin reaction. The time required for the precipitation was not determined. The buffer capacity of lectin and diphtheria antitoxin (computed from titration curves) was found to be 4.65 x 10^-5 Eqv/pH and 1.58 x 10^-4 Eqv/pH respectively. The titration curves also disclosed that,at this buffer power of the solutions and pH meter sensitivity of 0.03 pH units, the hydrogen ion produced or neutralized must be at least 1.14 Eqv/mole of active lectin and 2.66 Eqv/mole of active diphtheria antitoxin so that pH changes could be detected in those serological solutions. SUMMARY The pH following the reaction of two serological systems a. Plant hemagglutinin (lectin) and blood group A substance b. Diphtheria toxoid and diphtheria antitoxin was determined. No detectable change of pH was found on comparing the pH of the starting solutions with the pH found after mixing these serological solutions

Nature of postheparin plasma clearing factor

Thesis (Ph.D.)--Boston Universit

Single Stage Microinverter Based On Two-Switch DC-DC Flyback Converter

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Vascular dementia: Pharmacological treatment approaches and perspectives

Vascular dementia is a common condition for which there are no effective approved pharmacological treatments available. Absence of effective treatments creates a difficult situation for those suffering from the disease, their caregivers, and healthcare providers. This review will address our current understanding of the mechanisms of nerve cell damage due to ischemia and summarize available clinical trial data on several commonly used compounds including memantine, donepezil, galantamine, rivastigmine, nimodipine, hydergine, nicergoline, CDP-choline, folic acid, as well as such nonpharmacological approaches as validation therapy

Modeling of Trapped Fields by Stacked (RE)BCO Tape Using Angular Transversal Field Dependence

Stacks of superconducting (RE)BCO tape are gaining popularity as a potential alternative for superconducting bulks for trapped field applications. This is partly due to versatility and uniformity of the starting material, allowing for more deterministic prediction of field profile and magnitude. However, most FEM models of trapped field magnets do not incorporate parameters such as critical current and n-value dependence on the angle of applied magnetic field, leading to only qualitative modeling results. More quantitative results can be obtained from incorporating more data for superconductivity and thermal properties of the material. Such models can be used as a starting point for most geometries and both trapped field and current transport modeling problems. An FEM model of a stack of tapes was constructed using the H formulation, incorporating goniometric critical current and n-value measurements. The modeling results were compared to field cooling experiments for stacks of different heights. The experiment and modeling show good agreement.This work was supported in part by the Engineering and Physical Sciences Research Council, U.K., and in part by SKF S2M, France

Measurements of crossed-field demagnetisation rate of trapped field magnets at high frequencies and below 77 K

Design requirements of next generation electric aircraft place stringent requirements on the power density required from electric motors. Future prototype planned in the scope of European project “Advanced Superconducting Motor Experimental Demonstrator” ASuMED considers a permanent magnet synchronous motor, where the conventional ferromagnets are replaced with superconducting trapped field magnets, which promise higher flux densities and thus higher output power without adding weight. Previous work has indicated that stacks of tape show lower cross-field demagnetisation rate to bulk (RE)BCO whilst retaining similar performance for their size, however the crossed-field demagnetisation rate has not been studied in the temperature, magnetic field and frequency range that is relevant for the operational prototype motor. This work investigates crossed-field demagnetisation in 2G HTS stacks at temperatures below 77 K and frequency range above 10 Hz. This information is crucial in developing designs and determining operational time before re-magnetisation could be required

Stacks of high temperature superconducting tape as trapped field magnets for energy applications

The world demand for energy is estimated to increase by up to 70% from 2016 to 2040. To meet this demand in a sustainable way, the power density of electric motors and generators can be increased by using superconducting materials. In particular, trapped field superconducting magnets, where the field is generated by a circulating persistent current in the sample, can create magnetic fields an order of magnitude higher than possible using conventional ferromagnets, thus increasing the power density of motors and generators. This is of great interest where added weight comes at a premium, such as for naval propulsion motors, wind generators and motors/generators for future electric aircraft. This work investigates the suitability of stacked tape layers of second generation high temperature superconductors (HTS), such as YBa2Cu3O7-x (YBCO) for trapped field applications. The present limits for trapped field magnitude have been determined, which provide a basis for the optimization of pulsed field magnetization techniques for in-situ magnetization in motors and generators. Trapped fields were increased by optimising the magnetic pulse sequence, using thermally conductive material to reduce temperature rise during pulse and changing the duration of the magnetic field pulse. Finite element method computer modelling was used to model and predict the behaviour of the trapped field magnets made of HTS tape with good agreement to experiment for both field cooling and pulsed field magnetisation. The models rely on critical current data for the HTS tape and its dependence on magnetic field and temperature. For this reason, a critical current testing facility was developed and constructed as a part of this work capable of measuring critical current up to 900 A, magnetic field of 1.5 T and down to temperatures of ~10 K in forced and dynamically controlled helium vapour flow. Lastly, first steps into scaling up by pulse magnetising an array of HTS tape stacks were made, allowing for larger overall trapped flux values. Such an array exhibits geometry, similar to what is going to be used in a functional motor prototype being developed in our research group (Applied Superconductivity and Cryoscience Group, ASCG). The work done culminated in the highest trapped field achieved to date using both field cooling (13.4 T between two stacks) and pulsed field magnetization (2.1 T above a single stack), for this type of trapped field magnet

Analysis of an on-line superconducting cryofan motor for indirect cooling by LH2

This work relates to the study of an electrically powered cryofan for circulating close-loop cooling helium gas for superconducting applications with the following features: - Absence of any seal that can leak the pumped fluid or provide a path for heat transfer and require maintenance and/or is prone to failures. - The use of high temperature superconducting (HTS) stacks on the fan-rotor that, below critical temperature, can be magnetized contributing to the driving torque. The absence of electrically connected equipment as well as the lack of any seal, makes this arrangement especially suitable for reliable cryogenic helium gas circulation. Because HTS stacks cannot provide magnetic flux above Tc, during the initial stages of operation, in the presented study we analyse torque that will be provided by the passive iron components of the machine (reluctance torque, due to the saliency of the rotor) and by auxiliary permanent magnets or alternatively magnetizing coils

Computation of Superconducting Stacks Magnetization in an Electrical Machine

Superconducting technology offers the prospect of sharply increase the power density of rotating electrical machines, especially in the low speed, high torque range, with impact in applications such as wind energy and aircraft propulsion. Among the enabling technologies, stacks consisting of piling up layers of high temperature superconductor may provide a source of magnetic flux density for torque production, without the complexity of superconducting wound rotor poles. For this to happen, careful designs, optimizing electromagnetic, mechanical and thermal aspects at the same time, must be developed. In that sense, this work applies a recently developed combined electromagnetic formulation to compute the magnetization level of high temperature superconductor stacks installed in the airgap of an electrical motor after field cooling magnetization. The results are congruent with the applied field, show a strong interaction between teeth and stacks and provide a way of initializing the state of the machine prior to operation.Horizon 2020 research innovation programme under grant agreement No 7231119 (ASuMED consortium) and EPSRC grant EP/P000738/