Lee D. Hansen

A multiple-system, multi-channel diffusion denuder sampler for the determination of fine-particulate organic material in the atmosphere

Abstract Measurement of the loss of semi-volatile organic compounds from particles collected with a filter is carried out by comparing the amounts collected by comparable filter pack and diffusion denuder samplers. The sorbents used to collect organic compounds in the denuder and sorbent filters must have the same efficiency for collection of all gas-phase organic compounds present. Interpretation of the data requires that the efficiency of collection of gas-phase compounds by the denuder be known. In theory this can be accomplished by determination of the deposition pattern of all organic compounds collected in the denuder, but in practice this is very difficult if the organic material consists of a wide variety of compounds. An alternative approach is to determine the breakthrough of organic compounds in a sampler with a particle-collection filter preceding the denuder and sorbent filter. In such a sampler only gas-phase organic material enters the denuder. We have developed both a multi-channel parallel plate diffusion denuder sampler and a comparable sampler in which the denuder is preceded by a filter. Samples can be collected with the multisystem sampler at a flow rate of 35 sLpm. The denuder surfaces and the sorbent filters are made from sheets of an activated charcoal-impregnated filter paper. Collection of semi-volatile compounds by the samplers has been characterized and the systems have been field tested. The samplers are now being used for the routine collection and determination of semi-volatile organic compounds in particles at Canyonlands National Park in southeastern Utah. Available data from this field program show significant losses of particulate organic compounds on a quartz filter due to volatilization during sampling.

A respiration based description of plant growth rate responses to temperature

Abstract. The temperature dependence of metabolic rates determines how plant growth rates vary with temperature. This paper shows that equations on physiological relations between respiration rates (i.e. rates of heat loss and CO2 evolution) and growth rates can be used to describe temperature effects on plant growth rate. Incorporating measured values of plant respiratory heat and CO2 rates at a few temperatures into the equations allows description of growth rates as a function of temperature and provides a physiological basis for understanding the effects of temperature on growth rate. The paper presents data on cabbage (Brassica oleracea L. Capitata) and tomato (Lycopersicon esculentum Miller cv. Ace) as model cool-climate and warm-climate cultivars to illustrate application of the methods in determining optimal growth climates for different cultivars, accessions, and ecotypes. The respiration-based calculations of growth rate vs. temperature yield curves for both species that are consistent with known temperature-growth requirements. We conclude that plant responses to temperature can be accurately predicted in detail from respiration rate measurements and the growth-respiration model. These studies demonstrate that the temperature dependence of growth rates is a function of the temperature dependencies of both metabolic rates and metabolic efficiency, which change continuously with temperature. The ultimate cause of high- and low-temperature growth limits is commonly not membrane phase transitions or enzyme denaturation as has been supposed, but is loss of substrate carbon conversion efficiency. The results show that “plant temperature stress” has been misunderstood and must be redefined because there is no “nonstressfull temperature”.

Thermodynamics of binding of guest molecules to α- and β-cyclodextrins

Values of ΔG, ΔH, and ΔS are reported for the interaction of eighteen molecules and ions with α-cyclodextrin and of four molecules with β-cyclodextrin. The conclusions of this study are (1) the cyclodextrin–ClO4– complex has been shown to bind a cation, (2)α- and β-cyclodextrin have equilibrium constants for binding the same guest that are similar but the enthalpy and entropy changes are quite different in some cases, and (3) changes in ΔH are largely compensated for by changes in ΔS and it is suggested that this effect is due principally to the nature of the solvent, i.e. water.

Simultaneous measurement of metabolic heat rate, CO2 production, and O2 consumption by microcalorimetry

This study describes methods and equipment for measurement of metabolic heat rates of cells and tissues under conditions that provide simultaneous determinations of the flux rates of both O2 and CO2. Isothermal measurement of metabolic heats are conducted in a sealed ampule. A trapping solution is employed to absorb metabolic CO2. Absorption of CO2 produces heat at a rate proportional to the rate of CO2 production. Under these conditions, O2 consumption by the tissue results in a decrease in the partial pressure of O2 within the sealed ampule. The decrease in pressure can be monitored with a pressure sensor and related to O2 consumption rates. The combined measurements of heat rates, CO2, and O2 fluxes provide important information on bioenergetic efficiency of cell metabolism. These data can also suggest possible shifts in metabolic pathways or substrate sources as cells develop, or are exposed to effectors, inhibitors, and environmental factors.

Crystalline components of stack-collected, size-fractionated coal fly ash

As part of a program to characterize the fly ash which is emitted by coal-fired power plants, qualitative identification and quantitative estimation of the crystalline components of four size-fractionated and one unfractionated fly ash sample are reported. Although fly ash is mostly amorphous to X-rays, the presence of small amounts of quartz, hematite, mullite, gypsum, magnetite, and ferrite have been reported (1-3). However, quantitative determinations of these mineral phases have not been reported, nor have the crystalline phases been studied as a function of particle size. A knowledge of the Crystalline phases is of importance in the consideration of the potential health effects of inhaled particles. Because of the refractory nature of the quartz, mullite, and magnetite phases, these materials will have long residence times in the pulmonary region of the respiratory tract if they are deposited there ( 4 ) . Therefore, it is important to know the particle size distribution and concentrations of these materials in stack-collected coal fly ash. Furthermore, it is generally recognized that crystalline siliceous materials are more toxic than amorphous compounds of the same composition. Such particles are known to have significant effects on lung cells ( 5 ) and appear to be important toxicants to the pulmonary macrophage, the primary effector cell for lung immunosurveillance. Magnetite may also be a hazard to health because of its ability t o occlude biologically active transition-metal ions such as Mn and Ni by isomorphous substitution in the spinel crystal lattice (2). Magnetite could thus act as a slow release carrier agent for toxic elements. For this reason we have performed analyses of the magnetic phase for those metals which are likely to be associated with the magnetic fraction of the ash. The crystalline phases are important in determining the physical and chemical properties of the ash. Data on the crystalline phases may be useful in developing methods for resource recovery from, utilization of, and disposal of the ash (2). The mechanisms of formation of the various crystalline

New Precision Thermometric Titration Calorimeter

A new solution calorimeter is described which combines the thermometric titration techniques with the precision and accuracy of conventional solution calorimetry. The calorimeter through use of a unique design has a low heat leakage, k = 1.1×10−3 min−1, and a short equilibration period, 1–3 sec. Measurements of quantities of heat as small as 4 calories with an accuracy of 0.1% are possible. The heat of ionization of water at zero ionic strength has been determined to be 13.34±0.02 kcal/mole which is in excellent agreement with the value of 13.34±0.01 kcal/mole determined by conventional solution calorimetry. The large amount of information obtained from a single run makes this type of calorimeter a valuable addition to the field of solution calorimetry.

Plant calorimetry: how to quantitatively compare apples and oranges

Abstract Methods for the study of living plants or tissues by calorimetry have developed to the point that increasingly complex questions about plant physiology can be examined. Equipment now available or being developed for plant studies includes simple isothermal calorimeters with sample volumes from 1 ml to several liters, isothermal perfusion calorimeters, photocalorimeters, differential temperature scanning calorimeters, and calorimeters with multiple sample and CO 2 and O 2 sensing capabilities. Isothermal calorimetry, both with and without perfusion attachments, can be used to examine total metabolic rates of plant samples and to study effects of a wide variety of naturally occurring or artificially added factors on those rates. Moderately large numbers of plants can be examined for properties such as growth rates and tolerance limits to selected stimuli. Short term predictors of long term plant response can aid in selection of desired growth or tolerance characteristics and should prove of value in both classical plant breeding and future uses of biotechnology. Plant metabolism may be modeled with two inputs (photosynthate and oxygen) and three outputs (CO 2 , biomass, and heat). Understanding the transform function between input and output requires measuring at least four of the five parameters. Calorimetric measurements in conjunction with measurement of the other input-output parameters provides a quantitative understanding of metabolism in apples and oranges.

The relation between plant growth and respiration: A thermodynamic model

A thermodynamic model describing the relation between plant growth and respiration rates is derived from mass-and enthalpy-balance equations. The specific growth rate and the substrate carbon conversion efficiency are described as functions of the metabolic heat rate, the rate of CO2 production, the mean oxidation state of the substrate carbon produced by photosynthesis, and enthalpy changes for conversion of photosynthate to biomass and CO2. The relation of this new model to previous models based only on mass-balance equations is explored. Metabolic heat rate is shown to be a useful additional measure of respiration rates in plant tissues because it leads to a more explicit description of energy relations. Preliminary data on three Zea mays (L.) cultivars are reported. The model suggests new rationales for plant selection, breeding and genetic engineering that could lead to development of plants with more desirable growth rates.

Heat-loss corrections for small isoperibol-calorimeter reaction vessels☆

A more exact method of calculating the heat loss from isoperibol-calorimeter reaction vessels is described. This method involves corrections for changes in the heat-leak constant and the external power input with changes in the calorimeter contents, and is particularly important for reaction vessels with volumes of less than 25 cm3 or with heat-leak constants greater than about 0.005 min−1. The new calculation has been tested by application to results collected with a titration calorimeter of capacity 3 cm3.

Thermodynamics of proton ionization in dilute aqueous solution. Part XI. pK, ΔH°, and ΔS° values for proton ionization from protonated amines at 25°

A calorimetric study has been made of proton ionization from 69 protonated amines in aqueous solution at 25°. The resulting ΔH° values were combined with pK values to calculate ΔS° values. pK Values were obtained from the literature for 51 compounds and new values were determined for 18 compounds. A compilation of pK, ΔH°, and ΔS° values from the present study and the literature is given for proton ionization from 169 protonated amines. The effect of hydrocarbon chain length and branching on ΔH° and ΔS° values for proton ionization from primary and secondary aliphatic protonated amines is described by simple linear equations. Proton ionization for protonated amines was not found to follow the linear relation between ΔG° and ΔS° predicted by the Bjerrum theory of electrostatics. The changes in the ΔH° and ΔS° values from the first to the second step of ionization for 37 protonated diamines have been examined by using the Bjerrum and Kirkwood–Westheimer theories of electrostatic interactions in aqueous solution. A deviation identical to that previously found for dicarboxylic acids was found between the results derived from the experimental data and those predicted by the Kirkwood-Westheimer theory. Possible reasons for this deviation are discussed.