Showing papers by "Oregon State University published in 1991"

Contextual correlates of semantic similarity

Abstract: The relationship between semantic and contextual similarity is investigated for pairs of nouns that vary from high to low semantic similarity. Semantic similarity is estimated by subjective ratings; contextual similarity is estimated by the method of sorting sentential contexts. The results show an inverse linear relationship between similarity of meaning and the discriminability of contexts. This relation, is obtained for two separate corpora of sentence contexts. It is concluded that, on average, for words in the same language drawn from the same syntactic and semantic categories, the more often two words can be substituted into the same contexts the more similar in meaning they are judged to be.

Phosphorus limitation of primary productivity in the eastern Mediterranean Sea

Abstract: Although NO3- is generally considered to limit primary productivity in most of the world’s oceans, previous studies have suggested the Mediterranean Sea may be an exception. In this study of the southeastern Mediterranean, we found that all the PO43- was removed from the upper water column during the winter phytoplankton bloom in the core and boundary of a warm-core eddy, while measurable (0.3-0.6 µM) NO3- remained. The N:P (NO3-: PO43-) ratio in the core and boundary of the Cyprus eddy was 27.4 and the slope of the linear portion of the N vs. P scattergram with 25.5 with a positive intercept of 0.5 µM on the NO3- axis. A similar N:P ratio (28-29), slope (21-23), and intercept (0.9-1.1) was found for the water column across much of the southern Levantine basin. These data, taken together with the results of incubation experiments, lead us to conclude that the southeastern Mediterranean is strongly P limited. The degree of P limitation increases from west to east across the entire basin. We suggest that removal of PO43 by adsorbtion on Fe- rich dust particles may be an important process controlling the concentration of P in the water column.

Learning with many irrelevant features

Abstract: In many domains, an appropriate inductive bias is the MIN-FEATURES bias, which prefers consistent hypotheses definable over as few features as possible. This paper defines and studies this bias. First, it is shown that any learning algorithm implementing the MIN-FEATURES bias requires Θ(1/e ln 1/δ+ 1/e[2p + p ln n]) training examples to guarantee PAC-learning a concept having p relevant features out of n available features. This bound is only logarithmic in the number of irrelevant features. The paper also presents a quasi-polynomial time algorithm, FOCUS, which implements MIN-FEATURES. Experimental studies are presented that compare FOCUS to the ID3 and FRINGE algorithms. These experiments show that-- contrary to expectations--these algorithms do not implement good approximations of MIN-FEATURES. The coverage, sample complexity, and generalization performance of FOCUS is substantially better than either ID3 or FRINGE on learning problems where the MIN-FEATURES bias is appropriate. This suggests that, in practical applications, training data should be preprocessed to remove irrelevant features before being given to ID3 or FRINGE.

Bond lengths in free molecules of buckminsterfullerene, c60, from gas-phase electron diffraction.

Abstract: Electron diffraction patterns of the fullerene C 60 in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730°C. The many peaks of the experimental radial distribution curve calculated from the scattered intensity are completely consistent with icosahedral symmetry for the free molecule. On the basis of this symmetry assumption, least-squares refinement of a model incorporating all possible interatomic distances led to the values r g (C 1 -C 2 ) = 1.458(6) angstroms (A) for the thermal average bond length within the five-member ring (that is, for the bond fusing five- and six-member rings) and r g (C 1 -C 6 ) = 1.401(10) A for that connecting five-member rings (the bond fusing six-member rings). The weighted average of the two bond lengths and the difference between them are the values 1.439(2) A and 0.057(6) A, respectively. The diameter of the icosahedral sphere is 7.113(10) A. The uncertainties in parentheses are estimated 2σ values.

A corticosteroid receptor in neuronal membranes.

Abstract: Steroids may rapidly alter neuronal function and behavior through poorly characterized, direct actions on neuronal membranes. The membrane-bound receptors mediating these behavioral responses have not been identified. [3H]Corticosterone labels a population of specific, high-affinity recognition sites (dissociation constant = 0.51 nanomolar) in synaptic membranes from an amphibian brain. These binding sites were localized by receptor autoradiography in the neuropil, outside the regions of perikarya. The affinities of corticoids for this [3H]corticosterone binding site were linearly related to their potencies in rapidly suppressing male reproductive behavior. Thus, it appears that brain membranes contain a corticosteroid receptor that could participate in the regulation of behavior.

Systemic Endopolyploidy in Arabidopsis thaliana

Abstract: Microfluorometric analysis of the nuclear DNA contents of the somatic tissues of Arabidopsis thaliana has revealed extensive endoreduplication, resulting in tissues that comprise mixtures of polyploid cells. Endoreduplication was found in all tissues except those of the inflorescences and was developmentally regulated according to the age of the tissues and their position within the plant.

The nature of the cold filaments in the California Current system

Abstract: The velocity fields and water properties associated with cold filaments in the California Current are described on the basis of data from the Coastal Transition Zone experiment. Combined with previous field surveys and satellite imagery, these show seasonal variability with maximum dynamic height ranges and velocities in summer and minimum values in late winter and early spring. North of Point Arena in spring-summer, the flow field on the outer edge of the cold water exhibits the character of a meandering jet, carrying fresh, nutrient-poor water from the farther north on its offshore side and cold, salty, nutrient-rich water on its inshore side. At Point Arena in midsummer, the jet often flows offshore and continues south without meandering back onshore as strongly as it does farther north. At the surface, the jet often separates biological communities and may appear as a barrier to cross-jet transport, especially north of Point Arena in March-May.

Sverdrup revisited: Critical depths, maximum chlorophyll levels, and the control of Southern Ocean productivity by the irradiance‐mixing regime

Abstract: A reformulation of Sverdrup’s critical-depth calculation, using recent optical and physiological information, is developed and applied to data from the Southern Ocean. Comparisons between calculated critical depths (Zc) and mixed-layer depths (Zm) indicate that both the marginal ice zone and the open waters of the Antarctic Circumpolar Current provide favorable irradiance-mixing regimes for the initiation and early development of phytoplankton blooms in summer (i.e. Zc > Zm when phytoplankton biomass is low and the water clear; that when ice-edge blooms develop, Zc shoals to depths about equal to Zm implying that phytoplankton standing stocks in ice-edge blooms may be self-limiting as a result of reduced penetration of irradiance; and that the highest chlorophyll levels that can be sustained in summer in open waters not stabilized by meltwater are ∼ 1.0 µg liter‒1 in the Weddell and Scotia Seas and may be less in areas that experience stronger winds.

Data-parallel programming on MIMD computers

Abstract: The inadequacies of conventional parallel languages for programming multicomputers are identified. The C* language is briefly reviewed, and a compiler that translates C* programs into C programs suitable for compilation and execution on a hypercube multicomputer is presented. Results illustrating the efficiency of executing data-parallel programs on a hypercube multicomputer are reported. They show the speedup achieved by three hand-compiled C* programs executing on an N-Cube 3200 multicomputer. The first two programs, Mandelbrot set calculation and matrix multiplication, have a high degree of parallelism and a simple control structure. The C* compiler can generate relatively straightforward code with performance comparable to hand-written C code. Results for a C* program that performs Gaussian elimination with partial pivoting are also presented and discussed. >

An introduction to object-oriented programming

Abstract: From the Publisher: Discover the basic concepts of object-oriented programming and the elements of object-oriented design. Timothy Budd teaches objects, class methods, inheritance (including multiple inheritance), polymorphism and principles in a language-independent manner, with examples from five different languages: C++, Delphi, Java, Objective-C, and Smalltalk.

Factors and influences on high school students' career choices.

Abstract: Women continue to be disproportionately underrepresented in science and engineering fields. A model for career choice is proposed that includes both the direct and indirect effects that socializers can play in determining career choices. A sample of 2213 high school seniors from nine schools in Rhode Island were surveyed about their academic and career choices and the perceived influences on those choices. Parents and teachers were perceived to be influences on career choice more often for students (both men and women) choosing careers in engineering and science than for those not choosing such careers. Pay was a more important factor in career choice for men in general, and genuine interest was a more important factor for women not choosing careers in engineering or science. However, these gender differences do not appear among students with extremely strong mathematics and science coursework backgrounds, even though there remains a marked disparity in the proportion of men to women planning careers in engineering or science. Teachers may play a particularly important role in influencing the career choice of some of these women. Equity of access and encouragement in mathematics and science is certainly a necessary, but insufficient, condition for improving the representation of women in science and engineering.

The Leeuwin Current off Western Australia, 1986–1987

Abstract: The Leeuwin Current in the Indian Ocean off Western Australia differs from the other major eastern boundary currents, e.g., California Current, since it flows rapidly poleward against the prevailing equatorward wind. The first large-scale study of the Leeuwin Current was conducted between North West Cape (22°S) and the south-western corner of Australia (35°S) from September 1986 to August 1987. As part of this Leeuwin Current Interdisciplinary Experiment (LUCIE), current meters were deployed along the shelf-edge (from 22° to 35°S) and across the shelf and upper slope (at 29.5° and 34°S), and CTD surveys were made out from the shelf at several latitudes. Except for about one month (January) the flow between the surface and about 250 m was strongly poleward within 100 km of the shelf-edge, with a poleward transport of about 5 Sv (Sv ≡ 6 m3 s−1). The 325-day mean currents at the shelf-edge were poleward at about 10 cm s−1, opposing a mean equatorward wind stress of 0.3 dyn cm−2. The monthly mean cur...

Phylogenetic analysis of a natural marine bacterioplankton population by rRNA gene cloning and sequencing.

Abstract: The identification of the prokaryotic species which constitute marine bacterioplankton communities has been a long-standing problem in marine microbiology. To address this question, we used the polymerase chain reaction to construct and analyze a library of 51 small-subunit (16S) rRNA genes cloned from Sargasso Sea bacterioplankton genomic DNA. Oligonucleotides complementary to conserved regions in the 16S rDNAs of eubacteria were used to direct the synthesis of polymerase chain reaction products, which were then cloned by blunt-end ligation into the phagemid vector pBluescript. Restriction fragment length polymorphisms and hybridizations to oligonucleotide probes for the SAR11 and marine Synechococcus phylogenetic groups indicated the presence of at least seven classes of genes. The sequences of five unique rDNAs were determined completely. In addition to 16S rRNA genes from the marine Synechococcus cluster and the previously identified but uncultivated microbial group, the SAR11 cluster [S. J. Giovannoni, T. B. Britschgi, C. L. Moyer, and K. G. Field. Nature (London) 345:60-63], two new gene classes were observed. Phylogenetic comparisons indicated that these belonged to unknown species of alpha- and gamma-proteobacteria. The data confirm the earlier conclusion that a majority of planktonic bacteria are new species previously unrecognized by bacteriologists.

UV-B-Inducible and Temperature-Sensitive Photoreactivation of Cyclobutane Pyrimidine Dimers in Arabidopsis thaliana.

Abstract: Removal of cyclobutane pyrimidine dimers (CBPDs) in vivo from the DNA of UV-irradiated eight-leaf seedlings of Arabidopsis thaliana was rapid in the presence of visible light (half-life about 1 hour); removal of CBPDs in the dark, presumably via excision repair, was an order of magnitude slower. Extracts of plants contained significant photolyase in vitro, as assayed by restoration of transforming activity to UV-irradiated Escherichia coli plasmids; activity was maximal from four-leaf to 12-leaf stages. UV-B treatment of seedlings for 6 hours increased photolyase specific activity in extracts twofold. Arabidopsis photolyase was markedly temperature-sensitive, both in vitro (half-life at 30°C about 12 minutes) and in vivo (half-life at 30°C, 30 to 45 minutes). The wavelength dependency of the photoreactivation cross-section showed a broad peak at 375 to 400 nm, and is thus similar to that for maize pollen; it overlaps bacterial and yeast photolyase action spectra.

Antimicrobial effect of water‐soluble chitosans with high hydrostatic pressure

Abstract: Two commercially available water‐soluble chitosan salts, chitosan lactate and chitosan hydroglutamate, were examined for antagonistic effect against Escherichia coli V517, Staphylococcus aureus MF‐31 and Saccharomyces cerevisiae 15. Significant inactivation of each population was evident within 2 min of incubation with Chitosan. S. cerevisiae was the most sensitive of the microorganisms examined. Concentration effects varied but chitosan hydroglutamate was usually the more effective of the chitosans for inactivation of these microorganisms. Application of high hydrostatic pressure (2,380 atmospheres) to chitosan‐treated cultures of E. coli V517 or S. aureus MF‐31 resulted in additional inactivation but an amplified or synergistic effect was not found.

Response of Listeria monocytogenes and Vibrio parahaemolyticus to High Hydrostatic Pressure

Abstract: Listeria monocytogenes Scott A and CA, were subjected at 23°C to hydrostatic pressures ranging from 2,380 to 3,400 atm and Vibrio parahaemolyticus T-3765-1 from 680 to 1,700 atm. For L. monocytogenes Scott A, pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurization in phosphate-buffered saline (100 mM, pH 7.0). A population of about 106 CFU/mL L. monocytogenes was killed by exposure to 3,400 atm within 80 min at 23°C in UHT milk. A population of about 106 CFU/mL V. parahaemolyticus was killed by exposure to 1,700 atm within 10 min at 23°C in clam juice.

Ecological dynamics in the subarctic Pacific, a possibly iron-limited ecosystem

Abstract: It has been suggested that production in offshore waters of the subarctic Pacific is limited by availability of dissolved Fe. Although that is not yet adequately established, the functional consequences of the limitation (if it exists) can be characterized from the results of the Subarctic Pacific Ecosystem Research (SUPER) program. Fe limitation, or something like it, establishes a phytoplankton community dominated by very small cells. These plants are not limited by Fe availability. Rather, their production is limited by their stock and available illumination. Stock is set by microzooplankton grazers with rapid population growth rates and, thus, rapid response to increases in phytoplankton abundance. Micrograzers provide efficient recycling of nitrogen as NH,, and the ready availability of NH, sharply limits the annual utilization of NO,. Persistently high NO, concentrations result. Other possibly Fe-limited, oceanic ecosystems with persistently high, near-surface nutrients require similar, detailed analysis of ecosystem function.

An EPA program for monitoring ecological status and trends.

Abstract: Despite hundreds of millions of dollars spent annually in the United States on environmental monitoring, policy and decision makers seldom have ready access to monitoring data to aid in prioritizing reasearch and assessment efforts or to assess the extent to which current policies are meeting the desired objectives. EPA is currently conducting research to evaluate options for establishing an integrated, cooperative monitoring program, with participation by federal, state, and private entities, that could result in annual statistical reports and interpretive summaries on the status and trends in indicators of adverse disturbance and corresponding ‘health’ of the nation's ecosystem on the regional and national scale.

Identity of a second type of allatostatin from cockroach brains : an octadecapeptide amide with a tyrosine-rich address sequence

Abstract: An octadecapeptide that inhibits juvenile hormone synthesis has been isolated by HPLC from brain-retrocerebral complexes of the cockroach Diploptera punctata. The primary structure of this allatostatin has been elucidated by tandem mass spectrometry: Ala-Tyr-Ser-Tyr-Val-Ser-Glu-Tyr-Lys-Arg-Leu-Pro-Val-Tyr-Asn-Phe-Gly-Leu- NH2 (ASB2). The amidated three-residue C terminus of this type B allatostatin is identical to that of four known type A allatostatins, and the preceding three residues show close structural homology. ASB2 has over twice the activity of the type A tridecapeptide Ala-Pro-Ser-Gly-Ala-Gln-Arg-Leu-Tyr-Gly-Phe-Gly-Leu-NH2 (ASA1) in inhibiting juvenile hormone biosynthesis in corpora allata from females in early vitellogenesis (day 2), and its efficacy persists during pregnancy, but it is equally effective as ASA1 on glands from day-10 females (IC50 = 0.31 nM). The octadecapeptide is characterized by a potential dibasic cleavage site, Lys9-Arg10, the integrity of which is needed for high potency. The ASB2-(11-18)-octapeptide amide gives a full response at high concentrations at day 10 (IC50 = 48 nM), but the C-truncated (1-9)-, (1-11)-, and (1-17)-amide fragments of ASB2 are inactive. Thus, the endocrine message is located at the C terminus. N alpha-acetylation of the N-truncated (9-18), (10-18), and (11-18) fragments of ASB2 increases activity relative to the nonacetylated peptides. The site of action of type A and type B allatostatins is located before mevalonate kinase in the biosynthetic pathway for juvenile hormone.

Hope fault, Jordan thrust, and uplift of the Seaward Kaikoura Range, New Zealand

Abstract: In the northern South Island of New Zealand, displacement at the Pacific-Indian plate boundary is accommodated by the east-north-east-striking, right-lateral strike-slip Marlborough fault system. The southernmost Marlborough fault is the Hope fault; the late Pleistocene-Holocene horizontal slip rate on this fault is 20-25 mm/yr, about half of the rate of Pacific-Australian plate motion. Near the eastern end of the Hope fault, most displacement is transferred to the north-northeast-striking Jordan thrust, but the average dip-slip rate at the surface trace of this thrust is less than 4 mm/yr. We propose that most slip takes place on a blind thrust, expressed at the surface by the fault-propagation folding of the Seaward Kaikoura Range, and that the rate of uplift of this range is as high as that of the Southern Alps, 6 to 10 mm/yr. The major restraining bend of the Alpine fault has the same average slip rate as the Wairau fault, 4-6 mm/yr. Even though the Alpine fault is an east-dipping, reverse-separation fault at the restraining bend, this low slip rate results in uplift of the Spenser Mountains east of the bend at a rate lower than that of the Southern Alps and Seaward Kaikoura Range.

Optimal Product Layout in an Order Picking Warehouse

Abstract: The purpose of this paper is to provide a basis for locating product in an order picking warehouse such that average order picking time will be minimized. A stochastic model is developed to ensure that optimal, rather than just “good,” results are obtained. It is shown that, for a class of order picking warehouse, simple, but general, assignment algorithms may be used to optimally allocate product to locations. The results are then used to explore the effects of average order size and the shape of the inventory curve on order picking efficiency.

Error-correcting output codes: a general method for improving multiclass inductive learning programs

Abstract: Multiclass learning problems involve finding a definition for an unknown function f(x) whose range is a discrete set containing k > 2 values (i.e., k "classes"). The definition is acquired by studying large collections of training examples of the form 〈Xi, f(Xi)〉. Existing approaches to this problem include (a) direct application of multiclass algorithms such as the decision-tree algorithms ID3 and CART, (b) application of binary concept learning algorithms to learn individual binary functions for each of the k classes, and (c) application of binary concept learning algorithms with distributed output codes such as those employed by Sejnowski and Rosenberg in the NETtalk system. This paper compares these three approaches to a new technique in which BCH error-correcting codes are employed as a distributed output representation. We show that these output representations improve the performance of ID3 on the NETtalk task and of backpropagation on an isolated-letter speech-recognition task. These results demonstrate that error-correcting output codes provide a general-purpose method for improving the performance of inductive learning programs on multiclass problems.

Factors Limiting Aliphatic Chlorocarbon Degradation by Nitrosomonas europaea: Cometabolic Inactivation of Ammonia Monooxygenase and Substrate Specificity.

Abstract: The soil nitrifying bacterium Nitrosomonas europaea is capable of degrading trichloroethylene (TCE) and other halogenated hydrocarbons. TCE cometabolism by N. europaea resulted in an irreversible loss of TCE biodegradative capacity, ammonia-oxidizing activity, and ammonia-dependent O2 uptake by the cells. Inactivation was not observed in the presence of allylthiourea, a specific inhibitor of the enzyme ammonia monooxygenase, or under anaerobic conditions, indicating that the TCE-mediated inactivation required ammonia monooxygenase activity. When N. europaea cells were incubated with [14C]TCE under conditions which allowed turnover of ammonia monooxygenase, a number of cellular proteins were covalently labeled with 14C. Treatment of cells with allylthiourea or acetylene prior to incubation with [14C]TCE prevented incorporation of 14C into proteins. The ammonia-oxidizing activity of cells inactivated in the presence of TCE could be recovered through a process requiring de novo protein synthesis. In addition to TCE, a series of chlorinated methanes, ethanes, and other ethylenes were screened as substrates for ammonia monooxygenase and for their ability to inactivate the ammonia-oxidizing system of N. europaea. The chlorocarbons could be divided into three classes depending on their biodegradability and inactivating potential: (i) compounds which were not biodegradable by N. europaea and which had no toxic effect on the cells; (ii) compounds which were cooxidized by N. europaea and had little or no toxic effect on the cells; and (iii) compounds which were cooxidized and produced a turnover-dependent inactivation of ammonia oxidation by N. europaea. Images