Showing papers by "Oklahoma State University–Stillwater published in 1999"

Improving Nitrogen Use Efficiency for Cereal Production

Abstract: Worldwide, nitrogen use efficiency (NUE) for cereal production (wheat, Triticum aestivum L.; corn, Zea mays L.; rice, Oryza sativa L. and O. glaberrima Steud.; barley, Hordeum vulgare L.; sorghum, Sorghum bicolor (L.) Moench; millet, Pennisetum glaucum (L.) R. Br.; oat, Avena sativa L.; and rye, Secale cereale L.) is approximately 33%. The unaccounted 67% represents a $15.9 billion annual loss of N fertilizer (assuming fertilizer-soil equilibrium). Loss of fertilizer N results from gaseous plant emission, soil denitrification, surface runoff, volatilization, and leaching. Increased cereal NUE is unlikely, unless a systems approach is implemented that uses varieties with high harvest index, incorporated NH₄-N fertilizer, application of prescribed rates consistent with in-field variability using sensor-based systems within production fields, low N rates applied at flowering, and forage production systems. Furthermore, increased cereal NUE must accompany increased yields needed to feed a growing world population that has yet to benefit from the promise of N₂-fixing cereal crops. The Consultative Group on International Agricultural Research (CGIAR) linked with advanced research programs at universities and research institutes is uniquely positioned to refine fertilizer N use in the world via the extension of improved NUE hybrids and cultivars and management practices in both the developed and developing world. Contribution from the Okla. Agric. Exp. Stn.

Mirror symmetry and algebraic geometry

Abstract: Introduction The quintic threefold Toric geometry Mirror symmetry constructions Hodge theory and Yukawa couplings Moduli spaces Gromov-Witten invariants Quantum cohomology Localization Quantum differential equations The mirror theorem Conclusion Singular varieties Physical theories Bibliography Index.

Pseudomonas syringae Phytotoxins: Mode of Action, Regulation, and Biosynthesis by Peptide and Polyketide Synthetases

Abstract: Coronatine, syringomycin, syringopeptin, tabtoxin, and phaseolotoxin are the most intensively studied phytotoxins of Pseudomonas syringae, and each contributes significantly to bacterial virulence in plants. Coronatine functions partly as a mimic of methyl jasmonate, a hormone synthesized by plants undergoing biological stress. Syringomycin and syringopeptin form pores in plasma membranes, a process that leads to electrolyte leakage. Tabtoxin and phaseolotoxin are strongly antimicrobial and function by inhibiting glutamine synthetase and ornithine carbamoyltransferase, respectively. Genetic analysis has revealed the mechanisms responsible for toxin biosynthesis. Coronatine biosynthesis requires the cooperation of polyketide and peptide synthetases for the assembly of the coronafacic and coronamic acid moieties, respectively. Tabtoxin is derived from the lysine biosynthetic pathway, whereas syringomycin, syringopeptin, and phaseolotoxin biosynthesis requires peptide synthetases. Activation of phytotoxin synthesis is controlled by diverse environmental factors including plant signal molecules and temperature. Genes involved in the regulation of phytotoxin synthesis have been located within the coronatine and syringomycin gene clusters; however, additional regulatory genes are required for the synthesis of these and other phytotoxins. Global regulatory genes such as gacS modulate phytotoxin production in certain pathovars, indicating the complexity of the regulatory circuits controlling phytotoxin synthesis. The coronatine and syringomycin gene clusters have been intensively characterized and show potential for constructing modified polyketides and peptides. Genetic reprogramming of peptide and polyketide synthetases has been successful, and portions of the coronatine and syringomycin gene clusters could be valuable resources in developing new antimicrobial agents.

Dimensions, Determinants, and Differences in the Expatriate Adjustment Process

Abstract: We comprehensively test the Black, Mendenhall, and Oddou (1991) model of the dimensions and determinants of adjustment to international assignments. We also expand the model to examine two individual factors (i.e., previous assignments and language fluency) and three positional factors (i.e., hierarchical level, functional area, and assignment vector) as moderators of adjustment determinants. Surveys were completed by 452 expatriates from 29 different countries assigned to 45 host countries by large multinational firms. The multi-dimensionality of adjustment was investigated and confirmed. Support for the expanded Black et al. (1991) model was found. Several significant moderating effects emerged, showing different patterns of adjustment for those with different amounts of previous expatriate experience and levels of host country language fluency. Hierarchical level and assignment vector were also important moderators, but the effects for functional area were generally weak.

Edaphic factors and the landscape-scale distributions of tropical rain forest trees

Abstract: Tropical rain forests have the highest tree diversity on earth. Nonrandom spatial distributions of these species in relation to edaphic factors could be one mechanism responsible for maintaining this diversity. We examined the prevalence of nonrandom dis- tributions of trees and palms in relation to soil type and topographic position (''edaphic biases'') over a mesoscale (573 ha) old-growth tropical rain forest (TRF) landscape at the La Selva Biological Station, Costa Rica. All trees and palms $10 cm diameter were mea- sured and identified in 1170 circular 0.01-ha plots centered on an existing 50 3 100 m grid. Topographic position was classified for each plot, and slope and aspect were measured. Soil type data were taken from a previous study (Clark et al. 1998). A total of 5127 trees and palms were identified in 267 species. Detrended Correspondence Analysis and Canon- ical Correspondence Analysis showed that highly significant edaphic gradients were present, with swamp or highly fertile soils separated from the less fertile, well-drained upland soils. Species composition remained significantly related to topographic position when soil type was controlled for. The main floristic gradients were still significant when flooded sites were excluded from the analyses. Randomization tests on a weighted preference index were used to examine the relations of individual species to soil types and, within the dominant soil type, to topographic position. Of the 132 species with N $ 5 individuals, 33 showed significant associations with soil type. Within the dominant soil type, 13 of 110 analyzable species were nonrandomly associated with one or more topographic positions. For a variety of reasons, including issues relating to sample size and adequate edaphic characterization of landscapes, we suggest that the ;30% of species shown to be edaphically biased in this study is an underestimate of the true degree of edaphically related distri- butional biases. To evaluate this hypothesis will require mesoscale vegetation sampling combined with quantitative soil analyses at the same scale in a range of tropical rain forests. If edaphic distributional biases are shown to be common, this suggests that edaphically linked processes leading to differential recruitment are similarly common.

Attaining Decision Quality and Commitment From Dissent: The Moderating Effects of Loyalty and Competence in Strategic Decision-Making Teams

Abstract: Contradictory forces of dissent and consensus building attend the strategic decision process. Taking an information-processing perspective, we argue that two factors that affect perceptions of trus...

Electro-optic detection of terahertz radiation

Abstract: We present a complete frequency-domain description of electro-optic (EO) detection of terahertz (THz) electromagnetic radiation, including a description of the ellipsometry technique employed. These frequency-domain results show the effect of EO detection of a pulse of THz radiation as the product of three spectral filters acting on the complex amplitude spectrum of the THz pulse that is entering the EO crystal. For the usual experimental situation in which the optical bandwidth of the interrogating light pulse is small compared with the optical carrier frequency, we obtain an important simplification of our general result for the detected EO signal. When this simplified result is rewritten in the time domain, a more general description of the previous time-domain picture of EO detection is obtained.

M theory, topological strings and spinning black holes

Abstract: We consider M-theory compactification on Calabi-Yau threefolds. The recently discovered connection between the BPS states of wrapped M2 branes and the topological string amplitudes on the threefold is used both as a tool to compute topological string amplitudes at higher genera as well as to unravel the degeneracies and quantum numbers of BPS states. Moduli spaces of $k$-fold symmetric products of the wrapped M2 brane play a crucial role. We also show that the topological string partition function is the Calabi-Yau version of the elliptic genus of the symmetric product of $K3$'s and use the macroscopic entropy of spinning black holes in 5 dimensions to obtain new predictions for the asymptotic growth of the topological string amplitudes at high genera.

Effect of fermented milk (yogurt) containing Lactobacillus acidophilus L1 on serum cholesterol in hypercholesterolemic humans.

Abstract: Objective: Two controlled clinical studies were performed to examine effects of consumption of one daily serving of fermented milk (FM) (yogurt) on serum lipids.Methods: In the first study, subjects were randomly allocated to FM containing Lactobacillus acidophilus L1 of human origin or to FM containing L. acidophilus ATCC 43211 of swine origin. In this single-blind study, subjects consumed one 200 ml serving of FM daily for 3 weeks. The second study was a double-blind, placebo-controlled, cross-over study. Subjects completed a 4-week first treatment, had a 2-week washout, and completed a second 4-week treatment. In the second study subjects consumed FM containing L. acidophilus L1 or placebo FM over 4 weeks.Results: In the first study, FM containing L. acidophilus L1 was accompanied by a 2.4% (p<0.05) reduction of serum cholesterol concentration. In the second study, strain L1 reduced serum cholesterol concentration by 3.2% (p<0.05) in the first treatment period. In the second treatment period there were...

Appreciating similarities and valuing differences : The Miville-Guzman Universality-Diversity scale

Abstract: Universal-diverse orientation was defined as an attitude of awareness and acceptance of both the similarities and differences that exist among people. A 45-item scale developed to measure the construct was administered to 4 separate samples (ns = 93, 111, 153, and 135). Internal consistency and retest reliability for the Miville-Guzman Universality-Diversity Scale (M-GUDS) ranged from .89 to .95. The M-GUDS significantly correlated in theoretically predicted ways with measures of racial identity, empathy, healthy narcissism, feminism, androgyny, homophobia, and dogmatism (the last 2 correlations were negative). The M-GUDS displayed discriminant validity by failing to correlate with Scholastic Achievement Test Verbal scores, although mixed results were obtained with social desirability. In summary, the data suggest considerable reliability and initial construct validity for the M-GUDS.

Health of finishing steers: effects on performance, carcass traits, and meat tenderness.

Abstract: The impact of respiratory disease during a 150-d feedlot finishing period on daily gain, carcass traits, and longissimus tenderness was measured using 204 steer calves. Feedlot health status was monitored in two ways. First, clinical signs of respiratory infection were evaluated each day; treatment with antibiotic was based on degree of fever (if rectal temperature exceeded 40 degrees C then calves were treated). Steers that were treated (n = 102) had lower (P<.05) final live weights, ADG, hot carcass weights (HCW), less external and internal fat, and more desirable yield grades. Steers that were treated had a higher prevalence of carcasses that graded U.S. Standard than steers that were never treated. Second, as an alternative index of health status, lungs of all steers were evaluated at the processing plant using a respiratory tract lesion classification system; this health index included presence or absence of preexisting pneumonic lesions in the anterioventral lobes plus activity of the bronchial lymph nodes (inactive vs active). Lung lesions were present in 33% of all lungs and were distributed almost equally between treated (37%) and untreated cattle (29%). Steers with lesions (n = 87) had lower (P<.05) daily gains, lighter HCW, less internal fat, and lower marbling scores than steers without lesions. Compared to steers with lesions but inactive bronchial lymph nodes (n = 78), steers with lung lesions plus active lymph nodes had lower (P<.01) ADG and dressing percentage. Longissimus shear force values for steaks aged 7 d were lower (P = .05) from steers without lung lesions than those for steaks from steers with lung lesions. Overall, morbidity suppressed daily gains and increased the percentage of U.S. Standard carcasses. Compared to health assessment by clinical appraisal (based on elevated body temperature), classification based on respiratory tract lesions at slaughter proved more reliable statistically and, thereby, more predictive of adverse effects of morbidity on production and meat tenderness.

Study of the Response of a Biofilm Bacterial Community to UV Radiation

Abstract: We have developed a bioluminescent whole-cell biosensor that can be incorporated into biofilm ecosystems. RM4440 is a Pseudomonas aeruginosa FRD1 derivative that carries a plasmid-based recA-luxCDABE fusion. We immobilized RM4440 in an alginate matrix to simulate a biofilm, and we studied its response to UV radiation damage. The biofilm showed a protective property by physical shielding against UV C, UV B, and UV A. Absorption of UV light by the alginate matrix translated into a higher survival rate than observed with planktonic cells at similar input fluences. UV A was shown to be effectively blocked by the biofilm matrix and to have no detectable effects on cells contained in the biofilm. However, in the presence of photosensitizers (i.e., psoralen), UV A was effective in inducing light production and cell death. RM4440 has proved to be a useful tool to study microbial communities in a noninvasive manner.

Propagation of ultrawideband short pulses of terahertz radiation through submillimeter-diameter circular waveguides

Abstract: We report experimental investigations in which quasi-optical methods were used to efficiently couple freely propagating, optoelectronically generated, subpicosecond pulses of terahertz (THz) radiation into submillimeter circular metal tubes (waveguides) and, consequently, to measure the transmitted pulses from these waveguides. We observe very dispersive low-loss propagation over the frequency band from 0.65 to 3.5 THz, with frequency-dependent group velocities vg ranging from c/4 to c and phase velocities vp from 4c to c, where vgvp=c2. The linearly polarized incoming THz pulses couple significantly only into the TE11, TM11, and TE12 modes of the utilized 24- and 4-mm-long stainless-steel tubes, with inside diameters of 240 and 280 µm, respectively.

Involvement of the exopolysaccharide alginate in the virulence and epiphytic fitness of Pseudomonas syringae pv. syringae

Abstract: Alginate, a co-polymer of O-acetylated beta-1,4-linked D-mannuronic acid and L-guluronic acid, has been reported to function in the virulence of Pseudomonas syringae, although genetic studies to test this hypothesis have not been undertaken previously. In the present study, we used a genetic approach to evaluate the role of alginate in the pathogenicity of P. syringae pv. syringae 3525, which causes bacterial brown spot on beans. Alginate biosynthesis in strain 3525 was disrupted by recombining Tn5 into algL, which encodes alginate lyase, resulting in 3525.L. Alginate production in 3525.L was restored by the introduction of pSK2 or pAD4033, which contain the alginate biosynthetic gene cluster from P. syringae pv. syringae FF5 or the algA gene from P. aeruginosa respectively. The role of alginate in the epiphytic fitness of strain 3525 was assessed by monitoring the populations of 3525 and 3525.L on tomato, which is not a host for this pathogen. The mutant 3525.L was significantly impaired in its ability to colonize tomato leaves compared with 3525, indicating that alginate functions in the survival of strain 3525 on leaf surfaces. The contribution of alginate to the virulence of strain 3525 was evaluated by comparing the population dynamics and symptom development of 3525 and 3525.L in bean leaves. Although 3525. L retained the ability to form lesions on bean leaves, symptoms were less severe, and the population was significantly reduced in comparison with 3525. These results indicate that alginate contributes to the virulence of P. syringae pv. syringae 3525, perhaps by facilitating colonization or dissemination of the bacterium in planta.

A High Proportion of Bovine Blastocysts Produced In Vitro Are Mixoploid

Abstract: Fluorescence in situ hybridization with chromosome 6- and chromosome 7-specific probes was used to assess the extent of chromosome abnormalities in developing bovine blastocysts at 7-8 days after insemination in vivo or in vitro. Interphase nuclei (N = 10 946) were analyzed from 151 blastocysts produced in vitro and from 28 blastocysts recovered from superovulated animals. This revealed that 72% (109 of 151) of the in vitro-produced blastocysts were mixoploid, i.e., were a mixture of normal, diploid, and polyploid cells. However, only a small fraction of the total number of cells were chromosomally abnormal. Of the mixoploid blastocysts, 83% (91 of 109) contained less than 10% polyploid cells, 13% (14 of 109) contained 11-25% polyploid cells, and only 4% (4 of 109) of the blastocysts had more than 25% polyploid cells per blastocyst. In contrast, a significantly lower proportion (25%) of mixoploidy was found in 28 bovine blastocysts developed in vivo (p < 0.0001). All of the mixoploid blastocysts that had developed in vivo contained less than 10% polyploid cells. No entirely aneuploid blastocysts, i. e., blastocysts in which all cells had the same type of chromosome abnormality, were found in either of the groups. Taken together, the most common chromosome abnormalities observed were diploid-triploid mixoploidies and diploid-tetraploid mixoploidies. Thus, our results confirm earlier reports that morphologically normal bovine blastocysts developed in vivo are often mixoploids. We further show that in vitro-produced bovine blastocysts have a high rate of mixoploidy. Although the difference in mixoploidy rate detected in this study may not be general, it is an interesting phenomenon for further studies.

Layer-By-Layer Assembly of Core-Shell Magnetite Nanoparticles: Effect of Silica Coating on Interparticle Interactions and Magnetic Properties

Abstract: Monodisperse PS spheres were synthesized and packed into colloidal crystals by centrifugation as described previously [6]. Sphere diameters in various batches ranged from 420 ‐ 50 nm to 660 ‐ 30 nm. To prepare macroporous nickel oxide, nickel(II) acetate (2 g) was dissolved in either acetic acid (5 mL) or a mixture of H2O (5 mL)and ethanol (5 mL) at 60 C. After cooling to room temperature, any undissolved solid was removed by filtration. Centimeter-scale, close-packed, colloidal polystyrene crystals (1 g) were soaked in this solution for 3‐5 min. Excess solution was removed from the impregnated colloidal crystals by vacuum filtration. The samples were dried at 60 C for 2 h. The dried composites were soaked in 10 mL of a saturated solution of oxalic acid in ethanol (ca. 25‐30 g in 100 mL) for 3‐5 min. After additional vacuum filtration and drying, the PS spheres were removed by calcination in flowing air at 360‐575 C for 7‐10 h (heating rate: 1 C/ min). Macroporous Ni was prepared by heating macroporous NiO in flowing H2 at 300 C for 2‐5 h (heating rate: 1 C/min) or by heating the nickel oxalate/PS composite in flowing nitrogen at 450‐500 C for 10 h. Preparation of partially reduced samples containing both NiO and Ni was possible by decreasing the reduction time or temperature, or by carrying out a fast calcination, for example at 360 C for 1 h in fast flowing air. Electrochemical tests were performed in two electrode cells using 1 M aqueous KOH as the electrolyte and nickel pellets as both electrodes. Pellets were made by pressing a mixture of 10 wt.-% poly(vinylidene fluoride) binder with 90 wt.-% nickel to 1500 psi for 30 s. An SEM of the material indicated that a porous structure was still maintained. No carbon powder was needed to enhance the pellet conductivity. Impedance analysis was performed using a Solartron 1260 Impedance/Gain-Phase Analyzer along with a Solartron 1287 Electrochemical Interface. Other product characterization was carried out as described previously [6].

Not All Reading Disabilities Are Alike

Abstract: In this article, reading disability is defined broadly to refer to below-average achievement in reading comprehension as assessed by a standardized test. With our research we tried to answer the question of whether all children with reading disability share a common etiology of deficient phonology, or constitute heterogeneous groups. The answer to this question was sought in four studies that examined reading disabilities from the perspective of componential skills of reading. In Part 1, the results of the first study are reported. A principal-components analysis of the performance of 139 children from Grades 3, 4, and 6 on reading-related tasks yielded two factors: decoding and comprehension. However, factor analyses conducted for each grade separately indicated that orthographic skill and processing speed could possibly constitute a third component. The orthography-speed factor emerged as a factor only in the 6th grade. Part 2 of this article reports the findings of three studies that analyzed the componential skills profiles of poor readers. It was found that the poor readers constituted heterogeneous groups and that four different types of poor readers could be identified with deficiency in any one of the following skills: (a) decoding only, (b) comprehension only, (c) a combination of decoding and comprehension, and (d) a combination of orthographic processing and reading speed. It was also found that the criteria used in selecting poor readers influenced the distribution of the ratio of the four types of poor readers within any given group.

Web home pages as advertisements

Abstract: I f you belong to a commercial enterprise with a Web presence, how do you view your company’s home page? Frankly, your views do not matter. Like Richard Serra’s award-winning sculpture, which had to be removed from the New York City Federal Building in the face of public pressure, what really counts is what your audiences think about your home page. And we have reasons to believe that your audiences might be viewing your home page primarily as an advertisement designed to entice them to experience the site. At first glance, the proposition that a Web home page is an advertisement may seem somewhat farfetched. But thinking of a home page in advertising terms not only makes sense, it has far-reaching and profound implications for the design and evaluation of Web sites. In this article, we will flesh out the details of the home-page-as-an-ad proposition and describe the implications of this communications view. Web Home Pages as Advertisements Surendra N. Singh + Nikunj P. Dalal

Reference intervals and physiologic alterations in hematologic and biochemical values of free-ranging desert tortoises in the mojave desert

Abstract: Desert tortoise (Gopherus agassizii) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss, and human and disease-related mortality. Evaluation of hematologic and biochemical responses of desert tortoises to physiologic and environmental factors can facilitate the assessment of stress and disease in tortoises and contribute to management decisions and population recovery. The goal of this study was to obtain and analyze clinical laboratory data from free-ranging desert tortoises at three sites in the Mojave Desert (California, USA) between October 1990 and October 1995, to establish reference intervals, and to develop guidelines for the interpretation of laboratory data under a variety of environmental and physiologic conditions. Body weight, carapace length, and venous blood samples for a complete blood count and clinical chemistry profile were obtained from 98 clinically healthy adult desert tortoises of both sexes at the Desert Tortoise Research Natural area (western Mojave), Goffs (eastern Mojave) and Ivanpah Valley (northeastern Mojave). Samples were obtained four times per year, in winter (February/March), spring (May/June), summer (July/August), and fall (October). Years of near-, above- and below-average rainfall were represented in the 5 yr period. Minimum, maximum and median values, and central 95 percentiles were used as reference intervals and measures of central tendency for tortoises at each site and/or season. Data were analyzed using repeated measures analysis of variance for significant (P < 0.01) variation on the basis of sex, site, season, and interactions between these variables. Significant sex differences were observed for packed cell volume, hemoglobin concentration, aspartate transaminase activity, and cholesterol, triglyceride, calcium, and phosphorus concentrations. Marked seasonal variation was observed in most parameters in conjunction with reproductive cycle, hibernation, or seasonal rainfall. Year-to-year differences and long-term alterations primarily reflected winter rainfall amounts. Site differences were minimal, and largely reflected geographic differences in precipitation patterns, such that results from these studies can be applied to other tortoise populations in environments with known rainfall and forage availability patterns.

Direct measurement of the Wigner function by photon counting

Abstract: We report a direct measurement of the Wigner function characterizing the quantum state of a light mode. The experimental scheme is based on the representation of the Wigner function as an expectation value of a displaced photon number parity operator. This allowed us to scan the phase space point-by-point, and obtain the complete Wigner function without using any numerical reconstruction algorithms.

Neural networks for control

Abstract: Provides a quick overview of neural networks and explains how they can be used in control systems. We introduce the multilayer perceptron neural network and describe how it can be used for function approximation. The backpropagation algorithm (including its variations) is the principal procedure for training multilayer perceptrons; it is briefly described here. Care must be taken, when training perceptron networks, to ensure that they do not overfit the training data and then fail to generalize well in new situations. Several techniques for improving generalization are discussed. The article also presents several control architectures, such as model reference adaptive control, model predictive control, and internal model control, in which multilayer perceptron neural networks can be used as basic building blocks.

Burnout in counseling psychologists: Type of practice setting and pertinent demographics

Abstract: Extent of burnout experienced by conseling psychologists and the relationship between levels of burnout and different types of practice settings, selected demographic and work-related variables were investigated in this study. Burnout was defind in terms of the Maslach Burnout Inventory (MBI) subsxales. Multiple regression anslyses were perforned on the data (n = 521). Counseling psychologists in private practice reported the lowest levels of burnout, while those employed in hospital settings reported the highest levels of Burnout. A positive relationship was found between hours of client contact per week and sense of personal accomplishment. Finally, an inverse relationship was reported between age and burnout, and males experienced greater depersonalization of clients than females.