Showing papers by "University of Nebraska–Lincoln published in 1969"

Reproductive performance of 2-year-old Hereford and Angus heifers as influenced by pre-and post-calving energy intake.

Abstract: p REPARTUM and post-partum energy intake has been shown to influence reproductive performance of beef cows (Wiltbank et al., 1962, 1964). A low level of energy before calving was shown to delay onset of estrus following calving. Marked differences in conception rate were noted in cows on varying levels of energy following calving. Conception rate was decreased by low levels of energy after calving while cows which were full fed after calving had high conception rates. The results of these experiments were promising enough that further investigation seemed warranted. The experiment reported here was designed to determine the effects of two precalving and three post-calving levels of estimated digestible energy intake upon the reproductive performance of 2-yr.-old Hereford and Angus heifers nursing their first calves.

The Gravitational Field of a Disk

Abstract: The general solution of the static field equations of general relativity is given for a disk of "counterrotating" dust particles. The only nonvanishing components of the energy-momentum tensor are $T_{0}^{}{}_{}{}^{0}$ and $T_{\ensuremath{\chi}}^{}{}_{}{}^{\ensuremath{\chi}}$, which are assumed to have $\ensuremath{\delta}$-function singularities on the disk. Two representative families of solutions are considered, and it is shown that, for these solutions, physical considerations severely limit the strength of the gravitational potentials. The first family has surface density proportional to some power of $1\ensuremath{-}{\ensuremath{\rho}}^{2}$. Th requirement that the velocity of the dust particles should not exceed $c$ places a bound on the gravitational red-shift of $z=1.5803$ for these models. The second family is that of the uniformly rotating disks defined by ${v}^{2}={\ensuremath{\rho}}^{2}{\ensuremath{\omega}}^{2}{e}^{\ensuremath{-}4\ensuremath{\varphi}}$. Bardeen has pointed out that these disks can have arbitrarily large red-shifts without violating the velocity condition. However, it is shown that their red-shift cannot exceed 1.9015 before their binding energy becomes negative. This work suggests that the largest gravitational red-shift to which counter-rotating dust disks can give rise is of order of magnitude 1.

Particle Tracks in Emulsion

Abstract: A new theory of track formation in emulsion accounts for the tracks of charged particles on the basis of a theory developed earlier for the response of biological molecules and NaI(Tl) to energetic heavy ions. The probability that an emulsion grain will remain undeveloped when exposed to $\ensuremath{\delta}$ rays depositing a mean energy $\overline{E}$ is assumed to be ${e}^{\ensuremath{-}\frac{\overline{E}}{{E}_{0}}}$, where ${E}_{0}$ is the dose at which $\frac{1}{e}$ (37%) of the emulsion grains remain undeveloped, as in the one-or-more-hit cumulative Poisson distribution. The parameter ${E}_{0}$ incorporates variations in emulsion properties and processing conditions. Calculation of the spatial distribution of the ionization energy deposited by $\ensuremath{\delta}$ rays is combined with the assumed emulsion response to yield the spatial distribution of developed grains about the path of the charged particle. Calculations are in agreement with experimental data for grain counts (up to the relativistic rise), blackness profiles, and track width.

Personal Influence Networks and Voluntary Association Affiliation

Abstract: Individuals ordinarily have considerable information about voluntary associations even before they seriously think about joining a group In becoming affiliated, members usually rely on personal networks and often several persons are consulted When mass media sources are utilized in the affiliation process, they serve as a stimulus or catalyst (not one respondent in the sample joined an organization solely on the basis of mass media sources of information) Those with an extensive network of friends and relatives often become members through informal leaders Moreover, they are sought out and encouraged to join Individuals who have fewer primary-group resources frequently become members through formal leaders and themselves initiate the contact which results in membership Finally, personal influence networks are more likely to play an important role for those joining expressive rather than instrumental voluntary associations

Interference between coherent emissions in the measurement of atomic lifetimes.

Abstract: It is pointed out that the (zero-field) oscillations seen in the decay curves for atoms excited by beam-foil collisions may be due to interference of light from different fine-structure levels; the interference can only be seen, however, if light of different polarizations is detected with different sensitivity.

A Technique for the Rapid Measurement of Thermoelectric Power

Abstract: A new technique is described for rapid measurement of the thermoelectric power of rod‐shaped specimens over a wide temperature range. The apparatus utilizes sensitive commercial dc amplifier for the sample and temperature gradient voltages and a multiple‐point recorder for sampling these voltages as well as the sample temperature signal. The technique eliminates spurious thermal emf's in the leads and is based upon on‐the‐run recording of the sample and temperature gradient voltages as the temperature gradient slowly increases. As a test of this technique, the thermopower of pure nickel was measured between 4.2 and 300 K and the results are compared with other measurements using conventional techniques.

Teaching Principles of Economics Without Lectures.

Abstract: Lectures have generally been considered essential to good instruction. Indeed, some colleges have severely penalized truant students who dared absent themselves from the lecture hall. In this article, McConnell and Lamphear present important evidence that “students taking principles of economics with lectures, and those taking the course on a lectureless basis [perform] equally well on an intensive battery of objective examinations.”

Phospholipids from Bacillus stearothermophilus

Abstract: The lipids of Bacillus stearothermophilus strain 2184 were extracted with chloroform-methanol and separated into neutral lipid and three phospholipid fractions by chromatography on silicic acid columns. The phospholipids were identified by specific staining reactions on silicic acid-impregnated paper, by chromatography of alkaline and acid hydrolysis products, and by determination of acyl ester:glycerol:nitrogen:phosphorus molar ratios. The total extractable lipid was 8% of the dry weight of whole cells and consisted of 30 to 40% neutral lipid and 60 to 70% phospholipid. The phospholipid consisted of diphosphatidyl glycerol (23 to 42%), phosphatidyl glycerol (22 to 39%), and phosphatidyl ethanolamine (21 to 32%). The concentrations of diphosphatidyl glycerol and phosphatidyl glycerol were lower in 2-hr cells than in 4- and 8-hr cells. Whole cells were fractionated by sonic treatment and differential centrifugation. The total lipid content, expressed in per cent of dry weight of each fraction was: whole protoplasts, 10%; membrane fraction, 18%; 30,000 × g particulate fraction, 22%; and 105,000 × g particulate fraction, 26%. The relative phospholipid concentrations in each fraction were about the same. As had been previously reported, none of the phospholipid was stable to alkaline hydrolysis.

Interval Estimation of the Largest Mean of k Normal Populations with Known Variances

Abstract: A procedure is given for the construction of a fixed-width confidence interval of the largest mean of k(k≥1) normal populations with a common known variance, based on the largest sample mean. The sample size required to achieve the preassigned confidence coefficient can be computed by using the standard normal table only.

Projected Hartree Product Wavefunctions. II. General Considerations of Young Operators

Abstract: A discussion is given of the forms of two specific and one general Young operator for the irreducible representations of Sn important for fermion space functions. Comparisons are made of the projected Hartree product version of Lowdon's projected Hartree–Fock method with CI calculations.

Standing Waves on the Moon

Abstract: The existence of local annular and radial structures in the environment of lunar craters, and of a global selenographic tectonic pattern, is ascribed in part to standing “moonquakes” established after impact or eruption.

Microbiological Study of Water-Softener Resins

Abstract: Microbial identification using effluents backflushed from exhausted urban and rural tank resins and cleaned resins containing the sulfonated copolymer of styrene and divinylbenzene (SDB) were completed, along with microbial assessment of the concentrated stock salt brine. Forty-four different bacterial and fungal genera were identified. Extensive biochemical and animal virulence tests completed on one of the six bacterial salt brine isolates indicated a pathogenic staphylococcal strain. The retention of Staphylococcus aureus, a Flavobacterium sp, and Escherichia coli B bacteriophage was demonstrated both by using the nonexhausted sodium-regenerated resin and by using the same resin exchanged with different mono-, di-, and trivalent cations. Effluent counts completed after bacterial seepage through the resins indicated the Pb++ exchanged resin removed 55% of the bacteria; Na+, Fe++, and Al+++ removed 31 to 36% and Ca++ and Cu++ removed about 10 to 15%. Seventy per cent or more of the bacteriophage was removed by Fe++, Cu++, and Al+++, whereas the Ca++ and Na++ cations removed 25 to 31%. Over a 77-day period, nonsterile tap water was passed through bacterial seeded and uninoculated SDB (Na) resin columns. Effluent and resin elution counts demonstrated the growth and survival of 2 different bacteria per column. Increased bacterial retention, survival, and multiplication occurred concomitantly with accumulation of organic and inorganic materials and the Ca++ and Mg++ cations from the tap water. Furthermore, microbial elution from resin particles taken from column depths of 1, 8, and 16 cm indicated a bacterial diminution with increasing depths.

The influence of nitrogen and carbon sources on the production of glucoamylase by aspergilli

Abstract: Glucoamylase produced by Aspergillus niger was observed to increase in culture media at two specific intervals, namely, after three days and after six days of incubation. The lowest levels of enzyme production occurred when the nitrogen source was asparagine, trypticase or urea. Intermediate quantities of enzyme were formed when the fungi were grown on a nitrogen source of yeast extract. Corn steeping liquor and nutrient broth (2.5%) gave highest enzyme activity. The inorganic nitrogen source providing the best glucoamylase yield was ammonium-N. Nitrate-N or a mixture of ammonium-N and nitrate-N was less effective. When inorganic nitrogen was employed, the two periods of glucoamylase production were not as readily demonstrated. With ammonium-N, all the glucoamylase is produced during the fourth or fifth day of incubation, thus showing only one period of enzyme synthesis.The quantity of glucoamylase produced depended upon the monosaccharide added to the growth medium. Glucose yielded the highest level of enzyme regardless of the nitrogen sources. Mannose, usually, was slightly more effective than sorbitol and produced about half the quantity of glucoamylase obtained from glucose. Lowest levels of enzyme occurred when fructose or xylose served as carbon sources. Growth on 1.0 or 2.0% carbohydrate, rather than 5.0%, was found to result in higher levels of glucoamylase. Although A. niger NRRL 330 was the principle organism tested, the characteristics of glucoamylase synthesis were not specific for this strain since similar results were obtained with A. niger NRRL 3122 and A. awamori NRRL 3112.

Isolation of an ornithine-containing lipid from Thiobacillus thiooxidans.

Abstract: The ornithine-containing lipid was separated from the other lipids of Thiobacillus thiooxidans by thin-layer chromatography. The aminolipid possesses both amide and ester linkages.