Fh Values Research Articles

Effects of Shape, Size, and Air Velocity on Entry Loss Factors of Suction Hoods

This study further elucidated the effects of air velocity, aspect ratio (face length to face width), and area ratio (face area to duct area) on entry loss factors of suction hoods. A full scale ventilation system was utilized to determine the entry loss factor attributable to each of 20 square and rectangular hoods with a 90° included angle. Static and velocity pressures were measured using Pitot tubes connected by tubing to piezoresistive pressure transducers and inclined tube manometers. The entry loss factor, Fh, is the ratio of hood total pressure loss to mean velocity pressure. Values of Fh determined in this study ranged from 0.17–1.85. The values of Fh were a hyperbolic function of area ratio with a region rapidly increasing change for area ratios less than 5. For area ratios greater than 5, the values of Fh approached an asymptote of 0.17. Among hoods with a given area ratio (e.g., 2.5, 5.1, or 10.2), values of Fh were independent of aspect ratio. To a limited extent, Fh values decreased as mean air velocities increased from 319–1770 m/min (1046–5807 feet/min).

Effects of shape, size, and air velocity on entry loss factors of suction hoods.

This study further elucidated the effects of air velocity, aspect ratio (face length to face width), and area ratio (face area to duct area) on entry loss factors of suction hoods. A full scale ventilation system was utilized to determine the entry loss factor attributable to each of 20 square and rectangular hoods with a 90 degrees included angle. Static and velocity pressures were measured using Pitot tubes connected by tubing to piezo-resistive pressure transducers and inclined tube manometers. The entry loss factor, Fh, is the ratio of hood total pressure loss to mean velocity pressure. Values of Fh determined in this study ranged from 0.17-1.85. The values of Fh were a hyperbolic function of area ratio with a region rapidly increasing change for area ratios less than 5. For area ratios greater than 5, the values of Fh approached an asymptote of 0.17. Among hoods with a given area ratio (e.g., 2.5, 5.1, or 10.2), values of Fh were independent of aspect ratio. To a limited extent, Fh values decreased as mean air velocities increased from 319-1770 m/min (1046-5807 feet/min).

Relationship between heart rate and oxygen consumption during steady-state swimming in California sea lions.

Heart rate (fH) and rate of oxygen uptake (VO2) were measured in six subadult California sea lions Zalophus californianus while they were at rest and while they were swimming for 15 min at controlled speeds of up to 1.4 m s-1 and pulling loads of up to 3 kg. There was a good linear relationship between fH and VO2 in all six sea lions. The slopes of the individual regression lines varied between 2.66 and 4.36 beats ml-1 O2 kg-1, the intercepts varied between 48.2 and 63.0 beats min-1 and r2 varied between 0.82 and 0.93. The mean relationship for all six sea lions is fH = (57.4 +/- 2.0) + (3.58 +/- 0.23) VO2, r2 = 0.89 +/- 0.01. The mean of the lowest VO2 values was 5.1 +/- 0.4 ml min-1 kg-1 and the mean of the highest VO2 values was 26.9 +/- 1.9 ml min-1 kg-1. The means of the lowest and highest values of fH were less extreme, being 72 +/- 3 beats min-1 and 155 +/- 5 beats min-1, respectively. It is concluded that, by using data storage devices and grouped data, fH could be used in otariids as an indicator of aerobic metabolism under field conditions, in particular for breeding females during the period of lactation.

Thermal Processes for Metal Cans Compared to Retortable Plastic Containers

ABSTRACTComparison of the heating process and determination of the critical heating point was studied for homogeneous and nonhomogeneous products in 211 × 214 retortable plastic containers and metal cans. The fh, j, and Fo values for bentonite dispersions (4‐10%), were significantly different at α= 0.05 for the metal cans versus the plastic containers with metal lid oriented up or down. The slowest heating point was mathematically determined and found to be influenced by the container material and the lid orientation for the plastic containers. Results indicated the design of thermal processes in plastic containers must take into account nonsymmetrical external heat transfer due to the presence of the metal lid.

Laser induced fluorescence and vacuum ultraviolet spectroscopic studies of H-atom production in the dissociative recombination of some protonated ions

The flowing afterglow technique, coupled with laser induced fluorescence (LIF) and vacuum ultraviolet (vuv) absorption spectroscopy, has been used to determine the fractional H-atom contributions, fH, to the product distributions for the dissociative recombination of a series of protonated ions (N2H+, HCO+, HCO+2, N2OH+, OCSH+, H2CN+, H3O+, H3S+, NH+4, and CH+5 ) with electrons. The measurements were made at 300 K in two separate ways in two laboratories by (i) directly determining the H-atom number density using vuv absorption spectroscopy at the Lα (121.6 nm) wavelength and (ii) converting the H atoms to OH radicals using the reaction H+NO2→OH+NO followed by LIF to determine the OH number density. The agreement between the two techniques is excellent and values of fH varying from ∼0.2 (for OCSH+ ) to 1.2 (for CH+5 ) have been obtained showing that in some of the cases recombination can lead to the ejection of two separate H atoms. Comparison of the oxygen/sulphur analogs, HCO+2/OCSH+ and H3O+/H3S+ showed that the fH values were very different. Possible reasons for these differences are discussed. Comparison is also made with the available theory.

Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

ABSTRACTExperiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (fh) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.

Heating Rates of Thin-Profile Packages in Two Pilot-Scale Steam/Air Retorts

Heat transfer studies were carried out in two pilot scale steam/air retorts: a vertical positive-flow retort and a horizontal Lagarde retort, using rectangular test bricks of silicone rubber and nylon. The influences of steam content, temperature, flow-rate and flow-direction of the heating medium, package orientation, and entrapped air content in pouches on effective heating rates were evaluated. The study indicated the heating rate index, fh, to be significantly (p<0.05) influenced by steam content and temperature of the heating medium in the positive flow retort, and entrapped air in pouches under nonconstrained horizontal orientation while using both positive flow and Lagarde retorts. An air overpressure of 120kPa was found necessary to suppress the influence of entrapped gases during the processing. Heating of bricks in the vertical orientation resulted in higher fh values than in the horizontal orientation in some cases, while a reverse trend was observed in others.

Experimental Errors Associated with the Estimation of Thermal Diffusivity from Thermal Process Data

ABSTRACTAn increase in the accuracy and precision of thermal diffusivity (α) was observed when estimated from thermal process data using the analytical heat conduction equation as compared to using the process fh value. Differences in α for the two methods ranged from 2.4 to 3.5%. Correcting for the presence of the thermocouple probe became more important with smaller can sizes. The analytical solution to the heat conduction equation proved to be a very sensitive model with regard to prolonged retort come‐up time and heat conduction along the thermocouple probe.

Atomic Scattering Factors of Solid Elements

AbstractThe atomic scattering factor fh for elastic scattering of electromagnetic radiation depends strongly on electronic charge distribution n(r) in the atom. Deviations of recently measured fh's from those calculated from free‐atom electron states confirm the notion that n(r) gets appreciably modified in a solid. Recently it has been shown that the superposition of free‐atom charge densities through Löwdin's α‐expansion can help to find n (r) in a solid, which, in turn, yields a reasonable metallic cohesive energy and binary alloy formation energy. Here it is shown that the same procedure produces fh values that compare well with experiments as well as with more sophisticated band calculations.

A new approach to the measurement of X-ray structure amplitudes determined by thePendellösungmethod

The Laue-case rocking curve from two thin crystals is known to exhibit fine structure which can be used to determine the corresponding structure amplitude Fh. Thus F444 and F777 have been measured for crystalline silicon to a standard deviation of 0.2%. F444 is in excellent agreement with published experimental values. There are no previous high-precision measurements of F777 in the literature. The values measured seem to indicate that the accepted theoretical dispersion corrections are somewhat too low. A highly stable monolithic thin-wafer silicon dittractometer of a novel design was employed. Using an energy-dispersive solid-state detector and the white spectrum of a tungsten X-ray tube, rocking curves from a number of planes of the hhh family could be recorded simultaneously, thus reducing measurement time considerably and minimizing the influence of some sources of systematic and random error. Least-squares computer fitting of the theoretical curve to the complete measured one is employed to determine the value of Fh from the data. A complete discussion of the method is presented.

Critical Factors for Thermal Processing of Institutional Pouches

Institutional-sized pouches filled with whole kernel com in brine and condensed cream of celery soup were heated in a still retort. The sterilization values (Fo) and heat penetration parameters (j, fh, f2) were determined from temperature/time data as a function of the residual air in the horizontal pouches, pouch thickness, product fill, and circulation of the heating water. The Fo value for the soup was reduced from 11.5 to 2.5 min as the residual air in the pouch was increased to 250 ml The fh value nearly doubled as a result of the insulating effect of the air layer at the upper surface of the pouch, Eliminating the circulation of the heating water between the pouch layers increased the critical dimension for heat transfer and reduced the Fo for the soup to 0.6 min, an unacceptable value.

Water Velocity Effect on Heat Penetration Parameters During Institutional Size Retort Pouch Processing

ABSTRACTInstitutional size retort pouches (15 × 12 × 1) filled with 10% bentonite were processed in water with overriding air pressure. The heat penetration parameter, fh, was measured at seven flow rates from 10 gal/min (Re = 3000) to 110 gal/min (Re = 33000). Apparent convection heat transfer coefficients (h‐values) were calculated. Significant differences were found for both the h‐value and observed fh value as a function of flow rate. The h‐values ranged from 33–48 BTU/hr ft2 F and the observed fh values ranged from 23.0–20.1 min for 10 and 110 gal/min, respectively.

Rheology of suspensions of normal and hardened erythrocytes and their mixtures

The steady‐flow rheological properties of suspensions of mixtures of normal and glutaraldehyde‐hardened human red blood cells in albumin‐containing saline were determined in the shear rate range of 0.1–1500 sec−1, for total cell volume concentrations (hematocrits) between 30 and 43.5% and over the entire range of normal‐to‐hardened cell ratios. Suspensions of only hardened cells were Newtonian at lower shear rates, becoming dilatant at high shear rates. Suspensions of just normal cells were pseudoplastic, becoming Newtonian at high shear rates. Suspensions of mixtures of the two types of cells showed mixed behavior, dependent on the mixture composition. For suspensions with a constant total cell volume concentration, the apparent viscosity at a given shear rate is a nonlinear function of the fraction of the cells (fH) which are hardened. Below a critical value of fH, viscosity is a linear function of fH, but the slope is low. Above the critical fH, viscosity increases rapidly with fH. The critical fH is associated with a critical hardened cell volume concentration where interactions between hardened cells become significant. It is expected that steady‐flow rheological measurements usually will not provide a sensitive method for determining changes in erythrocyte deformability distribution in blood or related suspensions, unless the abnormal cells are rigid and greatly distorted from the normal cell shape.

10-Formyltetrahydrofolate Synthetase Activity in Normal and Brugia pahangi-Infected Aedes aegypti

The activity of 10-formyltetrahydrofolate synthetase (f1oFHS) in crude extracts of 4- to 5-day-old adult male and uninfected female Aedes aegypti was higher than that of other folate-related enzymes studied so far. L-Cysteine, Mg2?, and NH4? were required for optimal activity of this enzyme in the forward direction (forming f1oFH4, ADP and P1). The apparent Km values of the substrates and cofactors for the forward reaction showed correspondence between ATP and Mg2' (both 0.07 mM) and formate and NH? (13 mM and 7 mM); the apparent Km value of FH, (0.26 mM) corresponded closely to the Ki value of the 4-amino analog of folate methotrexate (0.24 mM), the latter being a competitive inhibitor of the enzyme. The estimated molecular weight of A. aegypti PfoFHS was 260,000. Two compounds were relatively strong inhibitors of the enzyme, as indicated by their IDo50 value: metho- trexate (2 CM) and suramin (8 /tM). The activity of PoFHS was approximately 40% lower in unin- fected female mosquitoes more than a week old than in those only 5 days old. The activity of this enzyme in female mosquitoes 7 days after they fed upon Brugia pahangi-infected jirds was approximately the same as that in age-matched uninfected females. However, the activity of fpoFHS in female mos- quitoes 12 days after infection with B. pahangi was 50% lower than that in age-matched uninfected fe- males. The significance of this latter finding is discussed.

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. III. The Effect of Metal Chlorides as Additives

Abstract This paper will describe the reaction of benzyl alcohol in the presence of various kinds of modified stabilized nickel catalysts, which had been prepared from the mother catalyst by treating it with solutions of appropriate metal chlorides. The catalytic activities of each modified catalyst for the formation of benzene, toluene, and benzaldehyde were compared in terms of the fH,fCH3, and fCHO values; the selectivities for the formation of benzene and toluene against that of benzaldehyde, SH and SCH3, were also evaluated. In general, the formation of toluene and benzene was greatly affected both by the kind and by the amount of metal chlorides used as additives. The reaction was promoted by the addition of a proper quantity of alkali metal chloride. In the cases of the reactions by lowlymodified catalysts, the decreasing order of the fH and fCH3 values according to the kind of metal ion adsorbed on the catalyst was as follows: Na+≥K+&amp;gt;Co2+&amp;gt;Ca2+&amp;gt;Cd2+&amp;gt;Ba2+&amp;gt;Hg2+&amp;gt;Cu2+. On the other hand, in the higher degrees of modification, the corresponding order of the fH and fCH3 values was altered to be as follows: K+&amp;gt;Na+&amp;gt;Co2+&amp;gt;Cd2+&amp;gt;Ba2+≥Ca2+&amp;gt;Cu2+&amp;gt;Hg2+. With regard to the modified nickel catalysts treated with 0.08 n solutions, it was found that the sequence of the fH and fCH3 values due to the kind of metal ion was roughly correlated with that of the atomic numbers of the corresponding metals. The results are discussed in connection with the general concept of catalytic chemistry.

The Catalytic Dehydrogenation, Dehydroxylation, and Dehydroxymethylation of Benzyl Alcohol. II. The Effects of Sodium Compounds as Additives

Abstract The reaction of benzyl alcohol has been examined over stabilized nickel (S-Ni) catalysts which have been modified by treating the catalyst surface with solutions of sodium compounds; this has been done in order to obtain some information about the relation between the behavior of the molecule adsorbed on the metal catalyst and the chemical nature of the catalyst surface. On the basis of the fH, fCH3, and fCHO values, which were defined as representing the catalytic activity for the formation of benzene, toluene, and benzaldehyde respectively, the variation in the activity for each modified S-Ni was evaluated. The general aspects may be summarized as follows: (1) The reaction is generally retarded with an increase in the amount of a sodium compound which is adsorbed on the catalyst during the modification process. (2) When the modification is of a lower grade, the effect of additives on the catalytic activity represented by f values is in the following order: NaNO3&amp;lt;NaOH&amp;lt;Na2S2O3&amp;lt;NaI&amp;lt;NaBr&amp;lt;NaCl. (3) A proper amount of NaCl on the catalyst promotes the reaction. The increase in SH and SCH3 values, which were defined as representing the selectivity factors for the formation of benzene and toluene toward that of benzaldehyde, is roughly associated with the increase in the corresponding f values.

Sterilization of Foods in Flexible Packages

Temperature distribution in an industrial scale ratort with specially designed rack for heat processing of flexible food packages was investigated. No significant difference of temperature distribution in the retort was observed between 105°C and 120°C of processing temperature. Horizontal rack system has almost same effect on heat penetration into packages containing 40% bentonite-60% water as substitute for food with vertical rack system proposed by LONG, F.E. The increase of partial air pressure in heating media resulted in the lowering of heat transfer rate; the fh value at 59.2% water vapor was higher than at 78.9% or 100%.

Solution Properties of Synthetic Polypeptides. III. Viscosity Behavior of Poly-γ-Benzyl-L-Glutamate in the Helix—Coil Transition Region

Limiting viscosity numbers [η] and specific rotations [α]578 of five samples of poly-γ-benzyl-L-glutamate (PBLG) (ranging in weight-average molecular weight M̄w from 1.9×104 to 4.0×105) in mixtures of dichloroacetic acid (DCA) and ethylene dichloride (EDC) of various compositions were measured as functions of temperature in the range where the PBLG molecule underwent a thermal transition from a disordered, random-coil state to an ordered helical state. For one sample the measurements of optical rotatory dispersion were made at various solvent compositions and temperatures, and the data were analyzed in terms of the Moffitt plot. When the M̄w of a given sample was above a certain critical value, [η] first decreased (or was kept constant), passed through a shallow minimum, and then increased sharply to a limiting value as the temperature was raised. Below the critical value, the change in [η] with temperature was a monotonic decrease. Irrespective of the molecular weight of the sample, [α]578 increased sharply in a narrow range near 30°C and then gradually leveled off as the temperature was raised. This narrow region coincided with the region where [η] underwent a marked increase. It was found that the helical content fH of a given sample can be evaluated from the reduced mean residue rotation measured at 578 mμ. When the values of [η] obtained under different solvent compositions and temperatures are plotted against the fH values so calculated, the plotted points formed a single composite curve over the entire range of fH. This curve exhibits a quite similar character to the theoretical curves for 〈S2〉 (mean-square radius of gyration) vs fH calculated by Nagai on the statistical-mechanical treatment of helix-forming polypeptides.

The determination of S-wave polarization angles for an earth model with crustal layering

Abstract This paper presents a method for determining the polarization angle of S waves which takes account of the crustal layering at the seismograph station. Charts are given for four crustal models, corresponding to normal continental, thick, and thin crusts, which enable one to obtain the polarization angle at the top of the mantle beneath the seismograph station. The equations to be used for obtaining the polarization angle are tan ∈ = F h tan γ tan ∈ = F v tan δ where ε is the polarization angle, γ is the angle between the horizontal component of the S-wave surface motion and the great circle path at the station, δ is the angle between the vertical axis and the component of the S-wave surface motion in the plane transverse to the great circle path, and Fh and Fv are functions of wave period, epicentral distance, and the crustal structure at the seismograph station. Values of Fh and Fv for four crustal models are given in the paper.

Factors Affecting Adsorption of Cations by Plant Roots

AbstractThe adsorption of Ca, Mg, K and Na by metabolically inactive H‐roots of wheat and alfalfa in relation to the nature of the anion has been studied. Titration curves and fH values showed wheat roots to have a weaker acid character than alfalfa roots. A high retention of H+ over metal cations was indicated. As a consequence, only small amounts of cations were adsorbed when offered as nitrates, but large amounts were adsorbed when offered as the bicarbonates. The order of increasing adsorption in either case was: Na, K, Mg, Ca.When Ca, Mg and K were offered in exchangeable form on a soil colloid with Ca/Mg and Ca/K ratios of 4, the Ca/Mg ratios on the roots were 4 and 8, and the Ca/K ratios were 10 and 24 for the wheat and alfalfa roots, respectively. The corresponding distribution of cations on the wheat roots were: Ca, 73%; Mg, 19%; K, 8%; and for alfalfa roots they were: Ca, 85%; Mg, 11%; and K, 4%.It is concluded that the adsorption of cations by metabolically inactive roots is a neutralization reaction involving principally Ca. The group of compounds involved in this reaction have been designated as RCOOH. Selective adsorption of cations involving exchange reaction, notably Mg and K, through RH is restricted to metabolically active roots. It is suggested that the proportions of K to Ca entering the plant is related to the concentration and proportion of RH to RCOOH of roots.