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Iowa State University

1990

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Matrix-Infrared Spectra Of Structural Isomers Of The Phosphorus Oxysulfide P4s3o, Zofia Mielke, Lester Andrews, Kiet A. Nguyen, Mark S. Gordon Dec 1990

Matrix-Infrared Spectra Of Structural Isomers Of The Phosphorus Oxysulfide P4s3o, Zofia Mielke, Lester Andrews, Kiet A. Nguyen, Mark S. Gordon

Mark S. Gordon

Photolysis of the P 4S3--03 molecular complex in solid argon with red light produced two sets of new infrared absorptions including terminal PO and symmetric P-S-P stretching modes, which are assigned to structural isomers of P4S30 with terminal oxygen at the apex and base phosphorus positions of P4S3. Further ultraviolet photolysis produced evidence for oxo-bridged P4S30 and a secondary product, P4S30 2.


Kinetics Of Random Sequential Adsorption Of Rectangles And Line Segments, R. Dennis Vigil, Robert M. Ziff Dec 1990

Kinetics Of Random Sequential Adsorption Of Rectangles And Line Segments, R. Dennis Vigil, Robert M. Ziff

R. Dennis Vigil

Random sequential adsorption of nonoverlapping rectangles of arbitrary orientation onto a continuous plane was investigated by computer simulation. It is shown that the approach to the jamming limit of rectangles with various aspect ratios obeys the scaling law OJ - O( T) - T - 1/3. Furthermore, the adsorption kinetics of rectangles approach those of line segments as the rectangle aspect ratio becomes large.


Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar Nov 1990

Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar

Richard Alan Lesar

The free energy simulation method is employed to study segregation to Σ5 and Σ13 (001) twist grain boundaries and their free energies in ordered Ni3−xAl1+x. In the temperature range studied (300–900K), it is shown that there is almost no segregation, strong Al segregation, and weak Ni segregation to the grain boundary for the stoichiometric, Al-rich, and Ni-rich bulk compositions respectively. It is also shown that the segregation is limited to a few (002) planes around the grain boundary and its magnitude decreases with increasing temperature. For Al-rich bulk composition, it is demonstrated that segregation at low temperature substantially lowers the …


Interaction Between The Component Enzymes Of The Glycine Decarboxylase Multienzyme Complex, David J. Oliver, Michel Neuburger, Jacques Bourguignon, Roland Douce Oct 1990

Interaction Between The Component Enzymes Of The Glycine Decarboxylase Multienzyme Complex, David J. Oliver, Michel Neuburger, Jacques Bourguignon, Roland Douce

David J. Oliver

The glycine decarboxylase multienzyme complex comprises about one-third of the soluble protein of the matrix of pea (Pisum sativum) leaf mitochondria where it exists at a concentration of approximately 130 milligrams protein/milliliter. Under these conditions the complex is stable with an approximate subunit ratio of 2 P-protein dimers:27 H-protein monomers:9 T-protein monomers:1 L-protein dimer. When the complex is diluted it tends to dissociate into its component enzymes. This prevents the purification of the intact complex by gel filtration or ultracentrifugation. In the dissociated state the H-protein acts as a mobile cosubstrate that commutes between the other three enzymes and shows …


Structure And Stability Of Hexacoordinated Sila Dianions, Mark S. Gordon, Marshall T. Carroll, Larry P. Davis, Larry W. Burggraf Oct 1990

Structure And Stability Of Hexacoordinated Sila Dianions, Mark S. Gordon, Marshall T. Carroll, Larry P. Davis, Larry W. Burggraf

Mark S. Gordon

The structures and stabilities of hexacoordinated silicon-containing dianions SiX6 2- have been investigated by using both ab initio (X= H, F) and semiempirical AMI (X= H, F, OH, Me, Cl) calculations. Both methods predict the hexacoordinated structures to be minima on the potential energy surfaces, although the semiempirical barriers for the reactions SiX6 2- -+ Six5- + x- appear to be rather overestimated based on the ab initio results for X = H, F. The positive charge on the central silicon atom actually increases as the number of ligands increases, and the role of d orbitals on that atom appears …


Theory Of Compositional And Magnetic Correlations In Alloys: Interpretation Of A Diffuse Neutron-Scattering Experiment On An Iron-Vanadium Single Crystal, J. B. Staunton, Duane D. Johnson, F. J. Pinski Sep 1990

Theory Of Compositional And Magnetic Correlations In Alloys: Interpretation Of A Diffuse Neutron-Scattering Experiment On An Iron-Vanadium Single Crystal, J. B. Staunton, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

We describe a first-principles theory for compositional and magnetic correlations in alloys and compare the results of the theory with recent diffuse, unpolarized, neutron-scattering measurements on a single crystal of ferromagnetic Fe0.865V0.135. The nuclear cross section is described very well by the theory and we are able to connect the q-dependent structure to the underlying electronic structure of the alloy. The magnetocompositional and magnetic correlations also may be obtained for comparison to polarized measurements.


Theoretical Study Of Pseudorotation Of Pentacoordinated Silicon Anions: The Prototypical Sih5-, Mark S. Gordon, Theresa L. Windus, Larry W. Burggraf, Larry P. Davis Sep 1990

Theoretical Study Of Pseudorotation Of Pentacoordinated Silicon Anions: The Prototypical Sih5-, Mark S. Gordon, Theresa L. Windus, Larry W. Burggraf, Larry P. Davis

Mark S. Gordon

Ab initio and semiempirical calculations are used to analyze the minimum energy path for the pseudorotation of SiH5-. Both AMI and MP2/6-31++G(d,p) predict pseudorotation barriers of 2.4 kcal/mol. A decomposition of the projected vibrational frequencies along the path is used to assist in the interpretation of the process.


Predicted Enthalpies Of Formation For Silaethylene, Disilene, And Their Silylene Isomers, Jerry A. Boatz, Mark S. Gordon Sep 1990

Predicted Enthalpies Of Formation For Silaethylene, Disilene, And Their Silylene Isomers, Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

Enthalpies of formation of silaethylene (SiH2=CH2), methylsilylene (HSiCH3), disilene (SiH2=SiH2), and silylsilylene (HSiSiH3) are predicted by using the recently developed GAUSSIAN-! method for computing accurate molecular energies. The predicted enthalpies of formation of the silylenes are compared with enthalpies of formation determined from isodesmic reactions. Very good agreement is found between these two methods and improved values for the enthalpies of formation of silaethylene and disilene are suggested.


Preparing For Africanized Honey Bees: Evaluating Control In Mating Apiaries, Richard L. Hellmich Ii, Gordon D. Waller Aug 1990

Preparing For Africanized Honey Bees: Evaluating Control In Mating Apiaries, Richard L. Hellmich Ii, Gordon D. Waller

Richard L Hellmich

A measure of queen mating control at an apiary is the number of matings with managed drones expressed as a percentage of total matings (managed and feral drones). In Texas, USA, using cordovan queens and drones for tests in July, it was found that at a commercial apiary near other apiaries 93% of all matings were with managed drones. At an isolated (outlying) apiary, the figure was 83%. It is estimated that in April-May, when most queens are produced in this area, mating control would be 96-98% and 93-96% respectively. It is concluded that 90-95% is a realistic level for …


Surface Moisture And Osmotic Stress As Factors That Affect The Sanitizing Of Beef Tissue Surfaces, James S. Dickson Aug 1990

Surface Moisture And Osmotic Stress As Factors That Affect The Sanitizing Of Beef Tissue Surfaces, James S. Dickson

James S. Dickson

The use of osmotic stress or desiccation in combination with 2% acetic acid reduced the numbers of Salmonella typhimurium or Listeria monocytogenes on beef tissue to a greater degree than the acid alone. Bacteria were osmotically stressed by NaCl, CaCl2, or sucrose solutions. Pre-washing with 20% NaCl followed by sanitizing with acetic acid reduced the numbers of S. typhimurium an additional 1.5-to 2-log cycles compared with acetic acid alone. Similar reductions were seen by allowing the tissue surfaces to dry before the application of the acid. Desiccation in combination with acetic acid was also effective in reducing the numbers of …


Theoretical Studies Of The Metallacyclopropenes C-[Mx2c2h2] (M = C, Sl, Ge, Sn; X = H, F), Jerry A. Boatz, Mark S. Gordon, Lawrence R. Sita Jul 1990

Theoretical Studies Of The Metallacyclopropenes C-[Mx2c2h2] (M = C, Sl, Ge, Sn; X = H, F), Jerry A. Boatz, Mark S. Gordon, Lawrence R. Sita

Mark S. Gordon

The geometries of the metallacyclopropenes c-[MX 2C2H2] (M = C, Si, Ge, Sn; X= H, F) are predicted by using the 3-21G(d) basis set and SCF wave functions. The nature of the ring bonding is investigated via analysis of the total electron density and is found to have little or no 11'-complex character. As a further probe of the electronic structure, bent bond lengths and intrinsic vibrational frequencies are computed. The classical barrier heights and the thermodynamics of the reaction MX 2 + HC==CH-- c-[MX 2C2H2] are predicted by using MP2/3-21G(d) energies.


Thermal Decomposition Processes For Sllanol, Mark S. Gordon, Lisa A. Pederson Jul 1990

Thermal Decomposition Processes For Sllanol, Mark S. Gordon, Lisa A. Pederson

Mark S. Gordon

Six alternative decomposition modes of silanol are examined with ab initio electronic structure theory. Geometries determined at the MP2/6-31 G( d,p) level of computation and single-point energetics obtained with MP4/MC-311 G{d,p) wave functions predict that the I, 1- and I ,2-eliminations of molecular hydrogen are both thermodynamically and kinetically competitive, with all other processes requiring at least 10 kcaljmol more energy to occur. At the highest level of theory, silanone is predicted to be 2.7 kcaljmollower in energy than hydroxysilylene.


Use Of A Bacteriocin Produced By Pediococcus Acidilactici To Inhibit Listeria Monocytogenes Associated With Fresh Meat, J. W. Nielsen, James S. Dickson, J. D. Crouse Jul 1990

Use Of A Bacteriocin Produced By Pediococcus Acidilactici To Inhibit Listeria Monocytogenes Associated With Fresh Meat, J. W. Nielsen, James S. Dickson, J. D. Crouse

James S. Dickson

A bacteriocin produced by Pediococcus acidilactici had an inhibitory and bactericidal effect on Listeria monocytogenes associated with fresh meat. MICs were significantly lower than minimum killing concentrations. When meat was inoculated with L. monocytogenes, the bacteriocin reduced the number of attached bacteria in 2 min by 0.5 to 2.2 log cycles depending upon bacteriocin concentration. Meat treated initially with the bacteriocin resulted in attachment of 1.0 to 2.5 log cycles fewer bacteria than that attained with the control. The bacteriocin, after 28 days of refrigerated storage on meat surfaces, was stable and exhibited an inhibitory effect on L. monocytogenes.


Total-Energy And Pressure Calculations For Random Substitutional Alloys, Duane D. Johnson, D. M. Nicholson, F. J. Pinski, B. L. Györffy, G. M. Stocks May 1990

Total-Energy And Pressure Calculations For Random Substitutional Alloys, Duane D. Johnson, D. M. Nicholson, F. J. Pinski, B. L. Györffy, G. M. Stocks

Duane D. Johnson

We present the details and the derivation of density-functional-based expressions for the total energy and pressure for random substitutional alloys (RSA) using the Korringa-Kohn-Rostoker Green’s-function approach in combination with the coherent-potential approximation (CPA) to treat the configurational averaging. This includes algebraic cancellation of various electronic core contributions to the total energy and pressure, as in ordered-solid muffin-tin-potential calculations. Thus, within the CPA, total-energy and pressure calculations for RSA have the same foundation and have been found to have the same accuracy as those obtained in similar calculations for ordered solids. Results of our calculations for the impurity formation energy, and …


Predicted Enthalpies Of Formation For Methyl-Substituted Disilanes, Jerry A. Boatz, Mark S. Gordon May 1990

Predicted Enthalpies Of Formation For Methyl-Substituted Disilanes, Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

Entha1pies of formation of the entire series of methyl-substituted disilanes, Si2(CH3)kH6_k (k = 1-6), are predicted by using homodesmic reactions at the MP2/6-31G(d)/ /RHF /3-21G* level of theory. The calculated values are systematically higher than the values suggested by Walsh but are in excellent agreement with the kinetic data of O'Neal, Ring, and co-workers.


Calculated Oscillator Strengths Between Vibrational Levels Of The Rotational And Trans-Bending Modes In The Ground And Lowest Excited States Of Disilene, Shiro Koseki, Mark S. Gordon May 1990

Calculated Oscillator Strengths Between Vibrational Levels Of The Rotational And Trans-Bending Modes In The Ground And Lowest Excited States Of Disilene, Shiro Koseki, Mark S. Gordon

Mark S. Gordon

Starting from the D2h structures of disilene and ethylene, the potential energy surfaces of the ground and excited singlet ( π → π) states along the rotational coordinate (au) and the trans-bending coordinate (b28) and the transition moments between these two states are calculated by using the multiconfigurational self-consistent-field (MCSCF) method with the 3-21G(d) basis set. Based on these results, the vibrational wave functions of these two states are expanded in Fourier series, and the Franck-Condon factors and the oscillator strengths are calculated between the vibrational levels of these two states. Though the transition moments are not constants along these …


The Kavousi-Thriphti Survey, 1988-1989, Margaret S. Mook, Donald Haggis Apr 1990

The Kavousi-Thriphti Survey, 1988-1989, Margaret S. Mook, Donald Haggis

Margaret S. Mook

Excavation was continued in four Late Minoan buildings on the north side of the Roussolakkos town site (Buildings 1 and 3-5). Building 1 was severely eroded but was fully revealed in outline, and good evidence was recovered for its history: founded in late LM lA, it replaced an MM IIB/LM lA structure in which metallurgical work in copper had taken place. Domestic activity (grinding grain and cooking) and some religious functions are among those suggested for the successive periods of later occupation (LM IB, LM II, and LM Ill). Building 3, adjacent to this, was much better preserved, up to …


Stratification Not Required For Tree-Of-Heaven Seed Germination, William R. Graves Jan 1990

Stratification Not Required For Tree-Of-Heaven Seed Germination, William R. Graves

William R Graves

Tree-of-heaven (Ailanthus altissima (Mill.) Swingle) seed germination and shoot dry weight were determined after stratifying samaras at 5 and 25 °C for up to 28 days. Seeds of samaras stratified at 5 °C for 0, 4, and 12 days showed 70, 77, and 96% germination, respectively, 7 days after sowing. Fourteen days after sowing, 90% of nonstratified seeds had germinated, but shoot weight of nonstratified seedlings was 16% less than that of seedlings from fruit stratified at 5 °C for 12 days. Germination 7 days after sowing was greater after stratification at 5 °C than at 25 °C, but the …


Flight Characteristics Of Foraging Africanized And European Honey Bees (Hymenoptera: Apidae), Robert G. Danka, Richard L. Hellmich Ii, Anita M. Collins, Thomas E. Rinderer, Vernon L. Wright Jan 1990

Flight Characteristics Of Foraging Africanized And European Honey Bees (Hymenoptera: Apidae), Robert G. Danka, Richard L. Hellmich Ii, Anita M. Collins, Thomas E. Rinderer, Vernon L. Wright

Richard L Hellmich

Interfloral movement and visitation parameters were quantified for individual Africanized and European honey bees (Apis mellifera) foraging in a field of sesame in Venezuela. The 2 bee types showed nearly identical movement and visitation characteristics for most of the parameters measured. Africanized bees spent slightly less time per flower visit (mean ± SD; 10±4 s vs. 12±6 s) and tended to travel at a slightly faster rate (210±150 cm/min vs. 180±120 cm/min.) The frequencies of visits for various resources differed; Africanized bees collected only pollen on 51% of visits and only nectar on 22% of visits, whereas for European bees, …


Introduction: Structural Properties For Determining Mechanisms Of Toxic Action, Steven P. Bradbury, Robert L. Lipnick Jan 1990

Introduction: Structural Properties For Determining Mechanisms Of Toxic Action, Steven P. Bradbury, Robert L. Lipnick

Steven P. Bradbury

The U.S. Environmental Protection Agency (EPA), under a variety of Federal legislation, is charged with the responsibility of assessing the hazards of chemicals to human health and the environment. In some cases EPA incorporates predictive techniques in its decisionmaking processes. In the context of some statutes, predictive toxicological methods can be cost-effective components in an overall approach for prioritizing chemicals for in-depth toxicological investigation. Predictive approaches are also used where empirical toxicological data are either unavailable or not required under a specific statute. For example, under Section 5 of the Toxic Substances Control Act (TSCA), EPA's Office of Toxic Substances …


Influence Of Cytochrome P450 Mixed-Function Oxidase Induction On The Acute Toxicity To Rainbow Trout (Salmo Gairdneri) Of Primary Aromatic Amines, Steven P. Bradbury, Joop L. M. Hermens, Steven J. Broderius Jan 1990

Influence Of Cytochrome P450 Mixed-Function Oxidase Induction On The Acute Toxicity To Rainbow Trout (Salmo Gairdneri) Of Primary Aromatic Amines, Steven P. Bradbury, Joop L. M. Hermens, Steven J. Broderius

Steven P. Bradbury

The influence of enzyme induction on the acute toxicity of aniline and 4-chloroaniline to rainbow trout (Salmo gairdneri) was investigated. For these two xenobiotics, bioactivation reactions are known to occur in mammals. Induction of cytochrome P450 mixed-function oxidase was obtained by intraperitoneal (ip) injection of trout with a mixture of polychlorinated biphenyls (Aroclor 1254). Five days after ip injection with three different doses of Aroclor 1254 (50. 100. and 200 mg/kg). benzo[a)pyrene hydroxylase activity in trout liver microsomes increased five- to sixfold. Cytochrome P450 concentrations in the microsomes were slightly. but significantly. enhanced in two of the three dose levels. …


Finite Temperature Structure And Thermodynamics Of The Au Σ5 (001) Twist Boundary, R. Najafabadi, D. J. Srolovitz, Richard Alan Lesar Jan 1990

Finite Temperature Structure And Thermodynamics Of The Au Σ5 (001) Twist Boundary, R. Najafabadi, D. J. Srolovitz, Richard Alan Lesar

Richard Alan Lesar

The structure and thermodynamic properties of a Σ5 (001) twist boundary in gold are studied as a function of temperature. This study was performed within the framework of the Local Harmonic (LH) model and employed an Embedded Atom Method (EAM) potential for gold. We find that for the Σ5 (001) twist boundary in gold, a distorted CSL structure is stable at low temperatures, but undergoes a phase transformation to a DSC related structure near room temperature. This transformation is shown to be first order. The temperature dependences of the excess grain boundary free energy, enthalpy, entropy, specific heat, and excess …


Evaluation Of Chicken Heterophil Adherence, Claire B. Andreasen, Kenneth S. Latimer, W. L. Steffens Jan 1990

Evaluation Of Chicken Heterophil Adherence, Claire B. Andreasen, Kenneth S. Latimer, W. L. Steffens

Claire B. Andreasen

Adherence of chicken heterophils was evaluated at 37 C using preconstructed columns containing various weights of nylon fiber (75 mg, 100 mg, or 125 mg) and whole blood anticoagulated with sodium heparin or 10% disodium ethylenediamine tetraacetic acid (EDTA). Additionally, 50-mg and 75-mg nylon fiber columns incubated at 41 C were used to evaluate heterophil adherence at an increased temperature. The mean percent adherence for heparin-anticoagulated blood applied to 75-mg, 100-mg, and 125-mg nylon fiber columns at 37 C was 76%, 92% and 97.4%, respectively. Samples applied to 50-mg and 75-mg columns at 41 C had adherence values of 27% …


Coincidence Orientations Of Crystals In Tetragonal Systems, With Applications To Yba2cu3o7, Abha Singh, N. Chandrasekhar, Alexander H. King Jan 1990

Coincidence Orientations Of Crystals In Tetragonal Systems, With Applications To Yba2cu3o7, Abha Singh, N. Chandrasekhar, Alexander H. King

Alexander H. King

We have developed a method for the characterization of coincidence-site lattices (CSL's) in tetragonal or near-tetragonal orthorhombic structures, by suitable modifications to the method of Grimmer & Warrington [Acta Cryst. (1987), A43, 232-243]. We have applied our method to determine coincidence rotations and the associated information appropriate for forming constrained CSL's in the high-To superconductor YBazCu307-n. The unit cell is orthorhombic with lattice parameters a = 3.82, b = 3"89 and c = 11.67 A for the nominal composition. We present tables of coincidence rotation angles, .Z, CSL, DSCL and associated step vectors up to ,~ = 50. We find …


Forage Quality Of Genetically Diverse Alfalfa Germplasms At Four Phenological Growth Stages, Andrew W. Lenssen, E. L. Sorensen, G. L. Posler Jan 1990

Forage Quality Of Genetically Diverse Alfalfa Germplasms At Four Phenological Growth Stages, Andrew W. Lenssen, E. L. Sorensen, G. L. Posler

Andrew W. Lenssen

Forage quality of various alfalfa (Medicago sativa L.) cultivars has been determined under different environmental conditions, and numerous trials with alfalfa have documented an inverse relationship between forage quality and maturity. Little information is available, however, regarding the comparative forage quality of the germplasm sources from which most USA cultivars were developed. We compared forage quality of these germplasm sources at four phenological stages under disease- and insect-free conditions in a greenhouse. Germplasm sources (cultivars) tested were: Indian (Sirsa # 9), African (African), Peruvian (Hairy Peruvian), Flemish (DuPuits), Turkistan (Lahontan), Chilean (Kansas Common), M. varia (Grimm), and Ladak (Ladak). Four …


Calculated Thermodynamic Properties And Phase Transitions Of Solid N2 At Temperatures 0≤T≤300 K And Pressures 0≤P≤100 Gpa, J. Belak, Richard Alan Lesar, R. D. Etters Jan 1990

Calculated Thermodynamic Properties And Phase Transitions Of Solid N2 At Temperatures 0≤T≤300 K And Pressures 0≤P≤100 Gpa, J. Belak, Richard Alan Lesar, R. D. Etters

Richard Alan Lesar

Thermodynamic properties of solid nitrogen are calculated over a variety of isotherms and isobars using a constant pressure Monte Carlo method with deformable, periodic boundary conditions. Vibron frequencies are calculated using a simple perturbation theory. In addition, pressure–volume relations, thermal expansion coefficients, structures, and phase transition pressures and temperatures are determined. In particular, the nature of the orientational disorder in the plastic crystal phases is examined by calculating a variety of orientational order parameters.


Location Of Melting Point At 300 K Of Nitrogen By Monte Carlo Simulation, Evert Jan Meijer, Daan Frenkel, Richard Alan Lesar, Anthony J.C. Ladd Jan 1990

Location Of Melting Point At 300 K Of Nitrogen By Monte Carlo Simulation, Evert Jan Meijer, Daan Frenkel, Richard Alan Lesar, Anthony J.C. Ladd

Richard Alan Lesar

We present an accurate new method to compute absolute free energies of molecular solids by computer simulations. As a first application, we computed the thermodynamicphase transition between the fluid phase and the orientational disordered solid β phase of nitrogen at 300 K, using a well tested pair potential. The computed coexistence pressure and the volume change coincides within the error margins with the experimental values. The coexistence volume differed by 2% from the experimental value. To our knowledge these results constitutes the first numerical calculation of the thermodynamic stability for a model of a realistic molecular solid.


Organ Hypertrophy And Responses Of Colon Microbial Populations Of Growing Swine To High Dietary Protein, James S. Dickson, Wilson G. Pond, Vincent H. Varel, Friday O. I. Anugwa, Gary S. Ross Jan 1990

Organ Hypertrophy And Responses Of Colon Microbial Populations Of Growing Swine To High Dietary Protein, James S. Dickson, Wilson G. Pond, Vincent H. Varel, Friday O. I. Anugwa, Gary S. Ross

James S. Dickson

Thirty-two castrated male crossbred growing pigs (average initial wt 26.9 kg) were used to determine the effect of a high level of dietary protein (37%) compared with a normal level of protein (15%) on enterobacteria and Campylobactersp. inhabitation in the large intestine and on visceral organ hypertrophy and the interrelationships between these two factors. Pigs were kept in pairs (eight pens of two pigs/diet) and fed their respective diets ad libitum. Eight pigs (two pens of two pigs fed each diet) were killed at wk 4, 8. 12 and 16 without fasting. Fecal samples were obtained every 2 wk from …


Transfer Of Listeria Monocytogenes And Salmonella Typhimurium Between Beef Tissue Surfaces, James S. Dickson Jan 1990

Transfer Of Listeria Monocytogenes And Salmonella Typhimurium Between Beef Tissue Surfaces, James S. Dickson

James S. Dickson

Beef tissue surfaces were inoculated with either Listeria monocytogenes or Salmonella typhimurium and placed in contact with uninoculated tissue surfaces. The transfer of bacteria from one surface to another was determined under conditions designed to simulate contamination during meat processing. Bacterial transfer decreased when the initial inoculum was allowed to adsorb to the base tissue prior to contact with the second tissue. The type of base tissue was a factor (P<0.05), with a greater transfer from fat with contact times of less than 1 min and a greater transfer from lean with longer contact times.


Comparison Of Homogenization By Blending Or Stomaching On The Recovery Of Listeria Monocytogenes From Beef Tissues, James S. Dickson Jan 1990

Comparison Of Homogenization By Blending Or Stomaching On The Recovery Of Listeria Monocytogenes From Beef Tissues, James S. Dickson

James S. Dickson

Homogenization by blending or stomaching was compared for the recovery of Listeria monocytogenes from inoculated intact beef tissue. There were no differences in numbers of recovered bacteria (P > 0.10) attributable to either homogenization time or method. Fewer viable bacteria (PcO.05) were recovered in phosphate buffer than either buffered peptone water or 2% trisodium citrate buffer. Tween 80 increased the numbers of bacteria recovered from fat tissue (PcO.05). Stomaching is an acceptable method for homogenizing samples for Listeria analysis.