Showing papers by "Iowa State University published in 1972"
TL;DR: In this article, a simple and precise method of assaying urease activity in soils is described, which involves determination of the ammonium released by urea-fixing activity when soil is incubated with tris(hydroxymethyl)aminomethane (THAM) buffer, urea solution, and toluene at 37°C for 2 h, ammonium release being determined by a rapid procedure involving treatment of the incubated soil sample with 2.5 M KC1 containing a urea inhibitor (Ag 2 SO 4 ) and steam distillation of
Abstract: A simple and precise method of assaying urease activity in soils is described. It involves determination of the ammonium released by urease activity when soil is incubated with tris(hydroxymethyl)aminomethane (THAM) buffer, urea solution, and toluene at 37°C for 2 h, ammonium release being determined by a rapid procedure involving treatment of the incubated soil sample with 2.5 M KC1 containing a urease inhibitor (Ag 2 SO 4 ) and steam distillation of an aliquot of the resulting soil suspension with MgO for 3.3 min. Studies reported showed that the optimal buffer pH and substrate (urea) concentration for assay of soil urease activity using THAM buffer are 9.0 and 0.02 M, respectively, and that the method described is satisfactory for assay of urease activity in ammonium-fixing soils.
776 citations
500 citations
TL;DR: It is concluded that abortion has been shown to occur at almost every point in development, and that probably more than one mechanism is involved.
Abstract: The studies reviewed date from 1925 to 1972 and contain extensive anatomical and cytological information all too often incomplete or vague. The terminology for microsporogenesis used is also often sketchy or inaccurate. An attempt therefore has been made to establish some consistency in microsporogenesis terminology via Fig. 1 and the tables. We have given, in convenient tabular form, CMS taxa, investigators, and the morphological and cytological events reported. By referring to a few keys, the reader can gain further insight into specific CMS taxa and can easily compare studies The work of Laser (1972) is only part of a more extensive investigation of the anatomy, cytology, and histochemistry of N and CMSSorghum bicolor (Laser, unpub.). To date, only a small part is published (Christensen, Horner & Lersten, 1972), but when completed it probably will be the most complete study to date of these aspects of CMS. Hoefert (1969a, 1969b, 1971) has investigated only normal microsporogenesis so far, but her intention also is to make a detailed descriptive comparison of N and CMS development. Such comparative electron microscope studies will be needed to help answer questions raised in the Introduction of this review. Concerning the events within microspores at the beginning of abortion, for example, there is complete ignorance of what organelle shows the first sign of disintegration or whether there is a definite sequence or simply a simultaneous collapse. The answer to this question could yield valuable clues to the direct cause of abortion Looking at the existing published studies and taking into account numerous examples of questionable technique and interpretation, we conclude that abortion has been shown to occur at almost every point in development, and that probably more than one mechanism is involved
344 citations
TL;DR: This is the first report of a protein endogenous to muscle that is able to catalyze degradation of the myofibril, and the very low level of unbound Ca2+ in muscle cells in vivo may regulate activity of this protein fraction, or alternatively, thisprotein fraction may be localized in lysosomes.
Abstract: Removal of rabbit psoas strips immediately after death and incubation in a saline solution containing 1 mM Ca2+ and 5 nM Mg2+ for 9 hr at 37°C and pH 7.1 causes complete Z-line removal but has no ultrastructurally detectable effect on other parts of the myofibril. Z lines remain ultrastructurally intact if 1 mM 1,2-bis-(2-dicarboxymethylaminoethoxy)-ethane (EGTA) is substituted for 1 mM Ca2+ and the other conditions remain unchanged. Z lines are broadened and amorphous but are still present after incubation for 9 hr at 37°C if 1 mM ethylenediaminetetraacetate (EDTA) is substituted for 1 mM Ca2+ and 5 mM Mg2+ in the saline solution. A protein fraction that causes Z-line removal from myofibrils in the presence of Ca2+ at pH 7.0 can be isolated by extraction of ground muscle with 4 mM EDTA at pH 7.0–7.6 followed by isoelectric precipitation and fractionation between 0 and 40% ammonium sulfate saturation. Z-line removal by this protein fraction requires Ca2+ levels higher than 0.1 mM, but Z lines are removed without causing any other ultrastructurally detectable degradation of the myofibril. This is the first report of a protein endogenous to muscle that is able to catalyze degradation of the myofibril. The very low level of unbound Ca2+ in muscle cells in vivo may regulate activity of this protein fraction, or alternatively, this protein fraction may be localized in lysosomes.
344 citations
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211 citations
TL;DR: In this article, the authors show that broadening of the Fermi distribution and volume strain caused by thermal expansion are the principal causes of the imaginary part of the dielectric constant.
Abstract: Thermotransmission and thermoreflection measurements were made on semitransparent films of Al, Au, and Cu at about 370 and 120 K in the range 0.5-5 eV. The data yield the thermomodulation spectrum $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{2}$ of the imaginary part of the dielectric constant directly, without Kramers-Kronig analysis. A comparison of the interband region of $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{2}$ for Cu with the piezo-modulation spectrum of a single crystal shows that broadening of the Fermi distribution and volume strain caused by thermal expansion are the principal causes of the $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{2}$ spectrum. The $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{2}$ spectrum for Al is particularly simple and can be discussed using closed-form expressions for the optical conductivity. It appears that the temperature dependence of the interband relaxation time for transitions across gaps produced by $|{V}_{111}|$ is smaller than that for transitions across gaps caused by $|{V}_{200}|$, which in turn is smaller than that for the infrared intraband transitions.
202 citations
TL;DR: In this paper, a model for B-starch is proposed, that employs intertwined (double) helices, and the small molecules of starch sirup can penetrate the interstices between crystallites and prevent strain build-up during drying.
Abstract: Although native B-type starch loses its sharp X-ray pattern on strong drying, the wet Nageli amylodextrin prepared from such starch gives a sharp B-pattern, that is only slightly reduced in sharpness by complete drying. Nageli amylodextrin dried admixed with a noncrystalline “filler” (e.g., starch sirup) gives an X-ray pattern essentially identical to that of the wet amylodextrin, except that the 16-A (No. 1) ring is greatly reduced in sharpness and intensity. Failure of the B-structure to collapse during drying indicates that water is not intercalated between turns of a helix or otherwise required to maintain the geometry and packing arrangement of the starch molecular chains. Rather, for native starch granules or amylose fibers, water relieves intercrystallite strains and consequent crystallite distortion induced by strong drying. For Nageli amylodextrin, the small molecules of starch sirup can penetrate the interstices between crystallites and prevent strain build-up during drying. For native starch granules, the interstitial regions are gel-like in character and less permeable to starch sirup molecules. A model for B-starch is proposed, that employs intertwined (double) helices.
190 citations
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01 Jan 1972179 citations
176 citations
TL;DR: Values suggested that most recommended chemical treatment levels for P. scabra on soybean in Iowa were suggested to be revised upward, and predictive equations to establish the relationship between soybean defoliation and subsequent yield loss were calculated by using data from previous hail-damage investigations.
Abstract: Developmental and feeding trials were conducted with Plathypena scabra (F.) under 3 sets of environmental conditions. Durations of the egg, larva, prepupa, pupa, and adult stages were 4.8, 18.7, 1.3, 9.4, and 9.3 days, respectively. Significant differences were found between trials for the egg and total life cycle, but no significant difference in larval stadium was indicated. Soybean leaf consumption of each larval instar was determined with a photometric device. The mean soybean-foliage consumption was 19.89 in2 per larva in trial 1 and differed significantly from the 17.06 in2 and 15.55 in2 obtained in trials 2 and 3. Estimates of total leaf area per soybean plant were made from field measurements. Predictive equations to establish the relationship between soybean defoliation and subsequent yield loss were calculated by using data from previous hail-damage investigations. Theoretical economic-injury levels for P. scabra on soybean in Iowa were calculated by using economists' cost and market data, agronomists' damage-yield data, and feeding data from this study. Calculated levels were 5.9, 18.3, 33.5, 28.7, and 40.5 larvae/row ft for soybean stages 1, 3, 5, 7, and 9, respectively. These values suggested that most recommended chemical treatment levels should be revised upward.
TL;DR: The renormalized-atom approach was used by Chodorow as mentioned in this paper to yield quantitative estimates of some of the essential potential-dependent parameters characterizing transition-metal band structures on the basis of essentially atomic considerations.
Abstract: The renormalized-atom approach, first used by Chodorow, is shown to yield quantitative estimates of some of the essential potential-dependent parameters characterizing transition-metal band structures on the basis of essentially atomic considerations. These are the position ${\ensuremath{\Gamma}}_{1}$ of the conduction-band minimum, the mean $d$-band energy, the energies associated with $d$-band extrema, and the degree of $s\ensuremath{-}d$ hybridization as defined within the Heine-Hubbard pseudopotential schemes. The estimates of ${\ensuremath{\Gamma}}_{1}$ and the $d$-band extrema utilize "renormalized-atom" band potentials within the Wigner-Seitz cell in which the interelectronic exchange is taken into account without resort to the ${\ensuremath{\rho}}^{\frac{1}{3}}$ approximation and incorporate the appropriate boundary conditions at the Wigner-Seitz radius ${r}_{\mathrm{WS}}$. The results have comparable accuracy with those obtained from augmented-plane-wave calculations employing the same crystal potential within the muffin-tin approximation. The band results are qualitatively similar to those obtained using more conventional ${\ensuremath{\rho}}^{\frac{1}{3}}$ potentials. The Wigner-Seitz viewpoint is thereby seen to be useful in obtaining quantitative results for certain high-symmetry points in $k$ space aside from ${\ensuremath{\Gamma}}_{1}$ with far less computational effort. In addition, the present scheme may provide a better starting point for dealing with $d\ensuremath{-}d$ exchange-correlation effects. Also discussed are a number of features general to the problem of constructing adequate transition-metal crystal potentials, in particular, how to deal with nonintegral $d$- and conduction-electron counts per atom, and configuration and/or multiplet averaging.
TL;DR: Development of a completely selective medium and continued study of agents inhibitory and stimulatory to propionibacteria would be a valuable aid in solving many of the practical problems associated with Swiss cheese manufacture.
Abstract: This review, appearing in three parts, is concerned with the growth, metabolism, and miscellaneous metabolic activities of propionibacteria. The first section, presented here, deals primarily with nutritional requirements, substrate and product inhibition, physical factors, associative action of other microorganisms, and enumeration and isolation of propionibacteria. The nutrition of propionic-acid bacteria has been extensively investigated and the absolute requirements for their nutrition are known. Since propionibacteria play an important role in the fermentation of Swiss cheeses, development of a completely selective medium and continued study of agents inhibitory and stimulatory to propionibacteria would be a valuable aid in solving many of the practical problems associated with Swiss cheese manufacture. Part two will discuss formation of propionate and acetate, the carboxylation, decarboxylation, and transcarboxylation reactions, the roles of biotin and vitamin B12, and the enzymes involved in the pr...
TL;DR: Temperature may be an important factor restricting the binding of α-actinin to the Z-line end of the F-Actin filament in vivo.
TL;DR: In this paper, sugar and uronic acid residues were derived from wall polysaccharides of oat (Avena sativa, var. Victory) coleoptiles by means of 2 N trifluoroacetic acid, 72% sulfuric acid or enzymic hydrolysis.
Abstract: Sugar and uronic acid residues were derived from wall polysaccharides of oat (Avena sativa, var. Victory) coleoptiles by means of 2 N trifluoroacetic acid, 72% sulfuric acid, or enzymic hydrolysis. The products of hydrolysis were reduced and acetylated to form alditol acetates which were analyzed using gas chromatography. Time-course studies of auxin-promoted changes in various wall fractions indicate that when exogenous glucose was available, increases in certain wall constituents paralleled increases in length. However, under conditions where exogenous glucose was not available, and where wall synthesis was limited, such correlations with growth were not apparent. Under these latter conditions total wall weight initially increased slightly, then decreased. These changes in weight were the net of increases in cellulose and some noncellulosic constituents and a decrease of over 75% in noncellulosic glucose. When coleoptile sections were preincubated without exogenous glucose for 8 hours to deplete endogenous wall precursors and subsequently treated with auxin, there were no detectable increases in wall weight. There was instead an auxin-promoted decrease in wall weight, and this decrease paralleled a decrease in noncellulosic glucose. There were no significant changes in other wall components. The auxin-promoted decreases in noncellulosic glucose are interpreted as a possible step in the mechanism of growth.
TL;DR: MPN (most-probable-number) counts of rhizobia by using legumes grown in plastic pouches were essentially equal to pour-plate counts.
Abstract: MPN (most-probable-number) counts of rhizobia by using legumes grown in plastic pouches were essentially equal to pour-plate counts. By using plastic pouches, 60 growth units could be placed in 684 cm2 of bench space, and only 20 minutes were required to prepare and seed 60 plastic pouches for inoculations.
TL;DR: From 2728 events of 205-GeV $ √ p √ n interactions found in 15,000 pictures taken with the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory, a total cross section of 39.1 mb was measured.
Abstract: From 2728 events of 205-GeV $\mathrm{pp}$ interactions found in 15 000 pictures taken with the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory, a total cross section of 39.5\ifmmode\pm\else\textpm\fi{}1.1 mb was measured. The mean charged-particle multiplicity for inelastic $\mathrm{pp}$ collisions was measured to be 7.65\ifmmode\pm\else\textpm\fi{}0.17. The prong distribution from 2 to 22 prongs is broader than a Poisson distribution and has a width parameter $f_{2}^{}{}_{}{}^{\ensuremath{-}}=〈{n}_{\ensuremath{-}}({n}_{\ensuremath{-}}\ensuremath{-}1)〉\ensuremath{-}{〈{n}_{\ensuremath{-}}〉}^{2}=0.95\ifmmode\pm\else\textpm\fi{}0.21$.
TL;DR: A strain of Escherichia coli K-12 bacteria is isolated that is believed to be conditionally defective in peptidyl-tRNA hydrolase, suggesting that the normal substrate is free for this enzyme.
Abstract: WE have isolated a strain of Escherichia coli K-12 bacteria that we believe to be conditionally defective in peptidyl-tRNA hydrolase. This enzyme (which we shall refer to as hydrolase) catalyses the hydrolysis of peptidyl-tRNA (or N-acyl-amino-acyl-tRNA) yielding free peptide (or N-acyl-amino-acid) and a tRNA capable of accepting its conjugate amino-acid1,2. In the current model of protein biosynthesis3 peptidyl-tRNA is the form in which the growing protein is bound to the ribosome. Ribosome-bound peptidyl-tRNA, however, is a poor substrate for the hydrolase2,4, implying that the normal substrate is free. N-acyl-aminoacyl-tRNAs occur in cells5–7 but the only species the function of which is known3,8, N-formyl-methionyl-tRNAf, is a poor substrate for bacterial peptidyl-tRNA hydrolase1,9,10.
TL;DR: In this paper, the Orion ammonia electrode can be used satisfactorily for determination of ammonium in soil extracts and water samples, and its results agree closely with those obtained by a distillation-titration method of determining ammonium.
Abstract: Interference and recovery tests reported indicate that the Orion ammonia electrode can be used satisfactorily for determination of ammonium in soil extracts and water samples. The electrode method of analysis described is rapid, simple, and precise, and its results agree closely with those obtained by a distillation‐titration method of determining ammonium in soil extracts and water samples.
TL;DR: Results were opposite on a final free-recall test; filled delay produced highest recall of terminal items and encoding and retrieval interpretations of the results were considered.
TL;DR: In this article, it was shown that LaAl2 behaves as a B.C.S. superconductor and the electronic specific constant, γ, is anomalously high compared to YAl2 and LuAl2.
TL;DR: In this paper, a review of structural optimization subject to dynamic constraints is presented, and suggestions for further work are offered, both methods for handling constraints on natural frequencies and methods for treating the more difficult constraints on quantities directly related to the dynamic response are discussed.
Abstract: Recent published research on structural optimization subject to dynamic constraints is reviewed, and suggestions for further work are offered. Both methods for handling constraints on natural frequencies and methods for treating the more difficult constraints on quantities directly related to the dynamic response are discussed. Computational aspects are emphasized throughout.
01 Jul 1972-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the embrittlement of vanadium and tantalum by hydrogen has been investigated with the ultimate goal being to answer three specific questions concerning ductility behavior in different temperature ranges.
Abstract: The embrittlement of vanadium and tantalum by hydrogen has been investigated with the ultimate goal being to answer three specific questions concerning ductility behavior in different temperature ranges. Torsion pendulum internal friction and another technique using the torsion pendulum as well as visual observations have been used to establish the solid solubility curve in the V-H and the Ta-H systems. The primary variables studied in this work were tensile strain rate, test temperature and hydrogen content. The results have been analyzed and tentative hypotheses have been set forth to explain the ductility behavior of the hydrogen charged metals.
TL;DR: In this article, α-actinin forms an extensive network of cross-connections between thin filaments in the I-band when incubated with Z-line-extracted fibrils at 0 °C.
TL;DR: It was concluded that ferricyanide procedure described is a reliable means of quantitatively determining the number of hemiacetal groups (reducing groups) for maltodextrins and α-1,4-polysaccharides when maltose is used as a standard.
01 Mar 1972
TL;DR: In this article, a simple steady-flow treatment of the spreading of a monolayer over a thin liquid film leads to χ 2 = (2h/μ)π 0 t, where χ is the distance spread in time t, h the liquid-film thickness, μ the coefficient of viscosity of the liquid underlying the monlayer, and π 0 is the spreading pressure of the lens (located at χ = 0 ) generating the monolayers.
Abstract: A simple steady-flow treatment of the spreading of a monolayer over a thin liquid film leads toχ 2 = (2h/μ)π 0 t, where χ is the distance spread in time t, h the liquid-film thickness, μ the coefficient of viscosity of the liquid underlying the monolayer, and π 0 is the spreading pressure of the lens (located at χ = 0 ) generating the monolayer. The spreading of oleic acid on glycerol films was followed by observation of talc markers, and found in remarkably good agreement with this simple equation. Limitations of the equation, associated with neglect of pressure gradients and idealization of flow patterns, are briefly discussed. The equation should be most nearly valid for thin, wide films, but even in this case idealizations involved in the theory are such that its success in representing data is surprisingly good.