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Showing papers by "Pennsylvania State University published in 1995"


Journal ArticleDOI
TL;DR: Weiner et al. as mentioned in this paper derived a new molecular mechanical force field for simulating the structures, conformational energies, and interaction energies of proteins, nucleic acids, and many related organic molecules in condensed phases.
Abstract: We present the derivation of a new molecular mechanical force field for simulating the structures, conformational energies, and interaction energies of proteins, nucleic acids, and many related organic molecules in condensed phases. This effective two-body force field is the successor to the Weiner et al. force field and was developed with some of the same philosophies, such as the use of a simple diagonal potential function and electrostatic potential fit atom centered charges. The need for a 10-12 function for representing hydrogen bonds is no longer necessary due to the improved performance of the new charge model and new van der Waals parameters. These new charges are determined using a 6-31G* basis set and restrained electrostatic potential (RESP) fitting and have been shown to reproduce interaction energies, free energies of solvation, and conformational energies of simple small molecules to a good degree of accuracy. Furthermore, the new RESP charges exhibit less variability as a function of the molecular conformation used in the charge determination. The new van der Waals parameters have been derived from liquid simulations and include hydrogen parameters which take into account the effects of any geminal electronegative atoms. The bonded parameters developed by Weiner et al. were modified as necessary to reproduce experimental vibrational frequencies and structures. Most of the simple dihedral parameters have been retained from Weiner et al., but a complex set of 4 and yj parameters which do a good job of reproducing the energies of the low-energy conformations of glycyl and alanyl dipeptides has been developed for the peptide backbone.

12,660 citations


Book
01 Jan 1995
TL;DR: In this article, Katok and Mendoza introduced the concept of asymptotic invariants for low-dimensional dynamical systems and their application in local hyperbolic theory.
Abstract: Part I. Examples and Fundamental Concepts Introduction 1. First examples 2. Equivalence, classification, and invariants 3. Principle classes of asymptotic invariants 4. Statistical behavior of the orbits and introduction to ergodic theory 5. Smooth invariant measures and more examples Part II. Local Analysis and Orbit Growth 6. Local hyperbolic theory and its applications 7. Transversality and genericity 8. Orbit growth arising from topology 9. Variational aspects of dynamics Part III. Low-Dimensional Phenomena 10. Introduction: What is low dimensional dynamics 11. Homeomorphisms of the circle 12. Circle diffeomorphisms 13. Twist maps 14. Flows on surfaces and related dynamical systems 15. Continuous maps of the interval 16. Smooth maps of the interval Part IV. Hyperbolic Dynamical Systems 17. Survey of examples 18. Topological properties of hyperbolic sets 19. Metric structure of hyperbolic sets 20. Equilibrium states and smooth invariant measures Part V. Sopplement and Appendix 21. Dynamical systems with nonuniformly hyperbolic behavior Anatole Katok and Leonardo Mendoza.

3,962 citations


Book
01 Jan 1995
TL;DR: This text intentionally omits theories of machine vision that do not have sufficient practical applications at the time, and basic concepts are introduced with only essential mathematical elements.
Abstract: This text is intended to provide a balanced introduction to machine vision. Basic concepts are introduced with only essential mathematical elements. The details to allow implementation and use of vision algorithm in practical application are provided, and engineering aspects of techniques are emphasized. This text intentionally omits theories of machine vision that do not have sufficient practical applications at the time.

2,365 citations


Journal ArticleDOI
TL;DR: In this article, the authors used time-resolved emission measurements of the solute coumarin 153 (C153) to probe the time dependence of solvation in 24 common solvents at room temperature.
Abstract: Time-resolved emission measurements of the solute coumarin 153 (C153) are used to probe the time dependence of solvation in 24 common solvents at room temperature. Significant improvements in experimental time resolution ({approx}100 fs instrument response) as well as corresponding improvements in analysis methods provide confidence that all of the spectral evolution (including both the inertial and the diffusive parts of the response) are observed in these measurements. Extensive data concerning the steady-state solvatochromism of C153, coupled to an examination of the effects of vibrational relaxation, further demonstrate that the spectral dynamics being observed accurately monitor the dynamics of nonspecific solvation. Comparisons to theoretical predictions show that models based on the dielectric response of the pure solvent provide a semiquantitative understanding of the dynamics observed. 156 refs., 26 figs., 5 tabs.

1,909 citations


Journal ArticleDOI
TL;DR: The purpose of this Update is to briefly summarize conceptual issues and recent developments in the study of root architecture and to propose a framework for understanding its physiological basis.
Abstract: Water and nutrient availability limit plant growth in a11 but a very few natural ecosystems. They limit yield in most agricultural ecosystems, and in the United States and other industrialized nations, intensive irrigation and fertilization have generated serious environmental problems. The acquisition of soil resources by plant root systems is therefore a subject of considerable interest in agriculture and ecology, as well as a complex and challenging problem in basic plant biology. Symbioses between roots and otlier organisms (notably mycorrhizas and N-fixing bacteria), modification of the rhizosphere through root exudates, and the uptake and transport characteristics of root axes are a11 important dimensions of this problem that are being actively researched by plant biologists. Another aspect of this problem that has received less attention, despite its probable importance, is root architecture. Recent methodological innovations present opportunities for improved under.standing of the functional importance of root architecture in the efficient acquisition of soil resources and plant adaptation to suboptimal soil conditions. The purpose of this Update is to briefly summarize conceptual issues and recent developments in the study of root architecture and to propose a framework for understanding its physiological basis.

1,627 citations


Journal ArticleDOI
TL;DR: McConahay et al. as mentioned in this paper compared factor structures of old-fashioned and modern sexism and racism and found that modern sexism is characterized by denial of continued discrimination, antagonism toward women's de-mands, and lack of support for policies designed to help women (for example, in education and work).
Abstract: Prejudice and discrimination against women has become increasingly subtle and covert (N. V. Be-nokraitis & J. R. Feagin, 1986). Unlike research on racism, little research about prejudice and dis-crimination against women has explicitly examined beliefs underlying this more modern form ofsexism. Support was found for a distinction between old-fashioned and modern beliefs about womensimilar to results that have been presented for racism (J. B. McConahay, 1986; D. O. Sears, 1988).The former is characterized by endorsement of traditional gender roles, differential treatment ofwomen and men, and stereotypes about lesser female competence. Like modern racism, modernsexism is characterized by the denial of continued discrimination, antagonism toward women's de-mands, and lack of support for policies designed to help women (for example, in education andwork). Research that compares factor structures of old-fashioned and modern sexism and racismand that validates our modern sexism scale is presented.

1,289 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied the spectrum of the volume in nonperturbative quantum gravity, and showed that the spectrum can be computed by diagonalizing finite dimensional matrices, which can be seen as a generalization of the spin networks.

1,212 citations


Journal ArticleDOI
TL;DR: The assumptions of a constructivist epistemology are described, they are contrasted with objectivist assumptions, and instructional systems that can support constructive learning at a distance are described.
Abstract: The fields of learning theory and instructional design are in the midst of a scientific revolution in which their objectivist philosophical foundations are being replaced by a constructivist epistemology. This article describes the assumptions of a constructivist epistemology, contrasts them with objectivist assumptions, and then describes instructional systems that can support constructive learning at a distance.

1,145 citations


Journal ArticleDOI
TL;DR: An initial contingency framework for OMIS development depending on the organization's environment and its life-cycle stage is proposed, and the relationships between an OMIS and organizational learning and decision making are discussed.
Abstract: Preservation of organizational memory becomes increasingly important to organizations as it is recognized that experiential knowledge is a key to competitiveness. With the development and widespread availability of advanced information technologies IT, information systems become a vital part of this memory. We analyze existing conceptualizations and task-specific instances of IT-supported organizational memory. We then develop a model for an organizational memory information system OMIS that is rooted in the construct of organizational effectiveness. The framework offers four subsystems that support activities leading to organizational effectiveness. These subsystems rest on the foundation of five mnemonic functions that provide for acquisition, retention, maintenance, search, and retrieval of information. We then identify the factors that will limit the success of OMIS implementation, although full treatment of this issue is outside the scope of the paper. To initiate a research agenda on OMIS, we propose an initial contingency framework for OMIS development depending on the organization's environment and its life-cycle stage, and discuss the relationships between an OMIS and organizational learning and decision making.

890 citations


Journal ArticleDOI
TL;DR: In this paper, the authors explored the concept of ecological sustainability and applied it to organizations by utilizing a systems framework and multiple levels of analysis, and the implications for ecological sustainability of dyadic relationships between the organization and entities at individual, organizational, political-economic, social-cultural, and ecological environment levels.
Abstract: This article explores the concept of ecological sustainability and applies it to organizations by utilizing a systems framework and multiple levels of analysis. The implications for ecological sustainability of dyadic relationships between the organization and entities at the individual, organizational, political-economic, social-cultural, and ecological environment levels are examined. Critical factors that influence the degree to which an organization's behaviors are ecologically sustainable are examined, and behavioral and structural elements that are likely to be manifested by ecologically sustainable organizations (ESOs) are suggested.

876 citations


Journal ArticleDOI
TL;DR: Since 1990, the Standardization and Terminology Committee of the International Society of Biomechanics has been working towards a recommendation for standardization in the reporting of kinematic data, and the use of center of mass-based segmental reference frames should be routinely used.

01 Jan 1995
TL;DR: In this article, meta-analytic methods were used to synthesize the results of published randomized, controlled-outcome studies of psychosocial interventions with adult cancer patients, including behavioral interventions, nonbehavioral counseling and therapy, informational and educational methods, organized social support provided by other patients, and other non-hospice interventions.
Abstract: Meta-analytic methods were used to synthesize the results of published randomized, controlledoutcome studies of psychosocial interventions with adult cancer patients. Forty-five studies reporting 62 treatment-control comparisons were identified. Samples were predominantly White, female, and from the United States. Beneficial effect size ds were .24 for emotional adjustment measures, .19 for functional adjustment measures, .26 for measures of treatment- and diseaserelated symptoms, and .28 for compound and global measures. The effect size of .17 found for medical measures was not statistically significant for the few reporting studies. Effect sizes for treatment-control comparisons did not significantly differ among several categories of treatment: behavioral interventions, nonbehavioral counseling and therapy, informational and educational methods, organized social support provided by other patients, and other nonhospice interventions. Though the field of psychosocial oncology is relatively young, intervention studies and indeed even narrative reviews of those studies are no longer rare. Meta-analytic investigations, however, are conspicuously absent from the literature. In the present article, the results of treatment-control studies of psychosocial interventions with adult cancer patients are assessed meta-analytically. The focus is on the effects of nonpharmacological interventions intended to improve the quality of life of adults who have already been diagnosed with

Journal ArticleDOI
TL;DR: To estimate approximate divergence times of species or species groups with molecular data, a method of constructing a linearized tree under the assumption of a molecular clock is developed and used to analyze hominoid mitochondrial DNA and drosophilid Adh gene sequences.
Abstract: To estimate approximate divergence times of species or species groups with molecular data, we have developed a method of constructing a linearized tree under the assumption of a molecular clock. We present two tests of the molecular clock for a given topology: two-cluster test and branch-length test. The two-cluster test examines the hypothesis of the molecular clock for the two lineages created by an interior node of the tree, whereas the branch-length test examines the deviation of the branch length between the tree root and a tip from the average length. Sequences evolving excessively fast or slow at a high significance level may be eliminated. A linearized tree will then be constructed for a given topology for the remaining sequences under the assumption of rate constancy. We have used these methods to analyze hominoid mitochondrial DNA and drosophilid Adh gene sequences.

Journal ArticleDOI
TL;DR: It is indicated that the combination of strength and endurance training results in an attenuation of the performance improvements and physiological adaptations typical of single-mode training.
Abstract: Thirty-five healthy men were matched and randomly assigned to one of four training groups that performed high-intensity strength and endurance training (C; n = 9), upper body only high-intensity strength and endurance training (UC; n = 9), high-intensity endurance training (E; n = 8), or high-intensity strength training (ST; n = 9). The C and ST groups significantly increased one-repetition maximum strength for all exercises (P < 0.05). Only the C, UC, and E groups demonstrated significant increases in treadmill maximal oxygen consumption. The ST group showed significant increases in power output. Hormonal responses to treadmill exercise demonstrated a differential response to the different training programs, indicating that the underlying physiological milieu differed with the training program. Significant changes in muscle fiber areas were as follows: types I, IIa, and IIc increased in the ST group; types I and IIc decreased in the E group; type IIa increased in the C group; and there were no changes in the UC group. Significant shifts in percentage from type IIb to type IIa were observed in all training groups, with the greatest shift in the groups in which resistance trained the thigh musculature. This investigation indicates that the combination of strength and endurance training results in an attenuation of the performance improvements and physiological adaptations typical of single-mode training.

Book
08 Jun 1995
TL;DR: Cognitive tool EduTech Wiki Learning with technology: Using computers as cognitive tools in Education cost and efficiency are reasons for using mindtools.
Abstract: Cognitive tool EduTech Wiki Learning with technology: Using computers as cognitive tools. In D. H Jonassen, David. H. Computers in the Classroom: Mindtools for Critical Thinking Using Mindtools in Education -THE Journal cost and efficiency are reasons for using mindtools. Computer Classroom: Mindtools for Critical Thinking. Jonassen, D. 2000. Computers as Mindtools Computers in the Classroom Marist Regional Computers in the Classroom 1:1 Computing program. The College is committed to equipping every student with their own computer by 2016. The 1:1 program

Journal ArticleDOI
TL;DR: Convergence theorems for the adaptive backpropagation algorithms are developed for both DRNI and DRNC and an approach that uses adaptive learning rates is developed by introducing a Lyapunov function.
Abstract: A new neural paradigm called diagonal recurrent neural network (DRNN) is presented. The architecture of DRNN is a modified model of the fully connected recurrent neural network with one hidden layer, and the hidden layer comprises self-recurrent neurons. Two DRNN's are utilized in a control system, one as an identifier called diagonal recurrent neuroidentifier (DRNI) and the other as a controller called diagonal recurrent neurocontroller (DRNC). A controlled plant is identified by the DRNI, which then provides the sensitivity information of the plant to the DRNC. A generalized dynamic backpropagation algorithm (DBP) is developed and used to train both DRNC and DRNI. Due to the recurrence, the DRNN can capture the dynamic behavior of a system. To guarantee convergence and for faster learning, an approach that uses adaptive learning rates is developed by introducing a Lyapunov function. Convergence theorems for the adaptive backpropagation algorithms are developed for both DRNI and DRNC. The proposed DRNN paradigm is applied to numerical problems and the simulation results are included. >

Journal ArticleDOI
01 Dec 1995-Genetics
TL;DR: A statistical method was developed for reconstructing the nucleotide or amino acid sequences of extinct ancestors, given the phylogeny and sequences of the extant species, and the new likelihood-based method was found to be superior to the parsimony method.
Abstract: A statistical method was developed for reconstructing the nucleotide or amino acid sequences of extinct ancestors, given the phylogeny and sequences of the extant species. A model of nucleotide or amino acid substitution was employed to analyze data of the present-day sequences, and maximum likelihood estimates of parameters such as branch lengths were used to compare the posterior probabilities of assignments of character states (nucleotides or amino acids) to interior nodes of the tree; the assignment having the highest probability was the best reconstruction at the site. The lysozyme c sequences of six mammals were analyzed by using the likelihood and parsimony methods. The new likelihood-based method was found to be superior to the parsimony method. The probability that the amino acids for all interior nodes at a site reconstructed by the new method are correct was calculated to be 0.91, 0.86, and 0.73 for all, variable, and parsimony-informative sites, respectively, whereas the corresponding probabilities for the parsimony method were 0.84, 0.76, and 0.51, respectively. The probability that an amino acid in an ancestral sequence is correctly reconstructed by the likelihood analysis ranged from 91.3 to 98.7% for the four ancestral sequences.

Journal ArticleDOI
TL;DR: In this article, a quantization of diffeomorphism invariant theories of connections is studied and the quantum diffeomorphicism constraint is solved and the space of solutions is equipped with an inner product that is shown to satisfy the physical reality conditions.
Abstract: Quantization of diffeomorphism invariant theories of connections is studied and the quantum diffeomorphism constraint is solved. The space of solutions is equipped with an inner product that is shown to satisfy the physical reality conditions. This provides, in particular, a quantization of the Husain–Kuchař model. The main results also pave the way to quantization of other diffeomorphism invariant theories such as general relativity. In the Riemannian case (i.e., signature ++++), the approach appears to contain all the necessary ingredients already. In the Lorentzian case, it will have to be combined in an appropriate fashion with a coherent state transform to incorporate complex connections.

Journal ArticleDOI
09 Mar 1995-Nature
TL;DR: The isolation of a new member of the immunoglobulin superfamily from the nurse shark, Ginglymostoma cirratum, is reported, which contains one variable and five constant domains and is found as a dimer in serum.
Abstract: IMMUNOGLOBULIN and T-cell receptor (TCR) molecules are central to the adaptive immune system. Sequence conservation, similarities in domain structure, and usage of similar recombination signal sequences and recombination machinery indicate that there was probably a time during evolution when an ancestral receptor diverged to the modern-day immunoglobulin and TCR1–3. Other molecules that undergo rearrangement have not been described in vertebrates, nor have intermediates been identified that have features of both these gene families. We report here the isolation of a new member of the immunoglobulin superfamily from the nurse shark, Ginglymostoma cirratum, which contains one variable and five constant domains and is found as a dimer in serum. Analyses of complementary DNA clones show extensive sequence diversity within variable domains, which is generated by both rearrangement and somatic diversification mechanisms. Our results suggest that rearranging loci distinct from immunoglobulin and TCR have arisen during evolution.

Journal ArticleDOI
TL;DR: In this article, the authors explore the possibility of efficacy-performance spirals in individuals, groups, and organizations, and consider compositional and cross-level effects by proposing factors that will moderate the relationship between spirals at different levels of analysis.
Abstract: This article explores the possibility of efficacy-performance spirals in individuals, groups, and organizations. Spirals are deviation-amplifying loops in which the positive, cyclic relationship between perceived efficacy and performance builds upon itself. Collective efficacy is defined, and upward and downward spirals are considered. Evidence from multiple levels of analysis is presented, and factors affecting the occurrence, continuation, and stopping of spirals are proposed. In addition, we consider compositional and cross-level effects by proposing factors that will moderate the relationship between spirals at different levels of analysis. Overall, 15 propositions are presented as guidelines for future research.

Proceedings ArticleDOI
29 May 1995
TL;DR: A duality theorem is proved explaining this intriguing performance and it is shown that there exists a “hidden” parameter that allows one to compute the reversal distance between signed permutations in polynomial time.
Abstract: Genomes frequently evolve by reversals r(i, j) that transform a gene order p1 ... pip i11 ... pj21pj ... pn into p1 ... pipj21 ... pi11p j ... pn. Reversal distance between permutations p and s is the minimum number of reversals to transform p into s. Analysis of genome rearrangements in molecular biology started in the late 1930's, when Dobzhansky and Sturtevant published a milestone paper presenting a rearrangement scenario with 17 inversions between the species of Drosophila. Analysis of genomes evolving by inversions leads to a combinatorial problem of sorting by reversals studied in detail recently. We study sorting of signed permutations by reversals, a problem that adequately models rearrangements in small genomes like chloroplast or mitochondrial DNA. The previously suggested approximation algorithms for sorting signed permutations by reversals compute the reversal distance between permutations with an astonishing accuracy for both simulated and biological data. We prove a duality theorem explaining this intriguing performance and show that there exists a "hidden" parameter that allows one to compute the reversal distance between signed permutations in polynomial time.

Journal ArticleDOI
TL;DR: A new basis on the state space of non-perturbative quantum gravity is introduced that allows a simple expression for the exact solutions of the Hamiltonian constraint (Wheeler-DeWitt equation) that have been discovered in the loop representation.
Abstract: We introduce a new basis on the state space of non-perturbative quantum gravity. The states of this basis are linearly independent, are well defined in both the loop representation and the connection representation, and are labeled by a generalization of Penrose's spin netoworks. The new basis fully reduces the spinor identities (SU(2) Mandelstam identities) and simplifies calculations in non-perturbative quantum gravity. In particular, it allows a simple expression for the exact solutions of the Hamiltonian constraint (Wheeler-DeWitt equation) that have been discovered in the loop representation. Since the states in this basis diagnolize operators that represent the three geometry of space, such as the area and volumes of arbitrary surfaces and regions, these states provide a discrete picture of quantum geometry at the Planck scale.

Journal ArticleDOI
TL;DR: In this article, the formation of self-assembled monolayers (SAMs) and multilayers on gold surfaces of rigid-rod conjugated oligomers that have thiol, cr,a.r-dithiol, thioacetyl, or cqor{'ithio-acetyl end groups' was analyzed usingillipsometry, X-ray photoelectron spectroscopy Q(PS), and infrared extemal reflectance spec6oscopy.
Abstract: This paper describes tudies of the formation of self-assembled monolayers (SAMs) and multilayers on gold surfaces of rigid-rod conjugated oligomers that have thiol, cr,a.r-dithiol, thioacetyl, or cqor{'ithioacetyl end groups' The SAMs were analyzed usingillipsom-etry, X-ray photoelectron spectroscopy Q(PS), and infrared extemal reflectance spec6oscopy. The thiol moieties usually dominate adsorption on the gold sites; interactions with the conjugated z-systems are weaker. Rigid rod cr,al-dithiols form *r"*bli"r in which one thiol gouP binds to the surface while the second thiol moiety projects upward at the exposed surface of the SAlvl. ln sinr deprotection of the thiol moieties by deacylation of thioacetyl groups using NFlaOFtpermits formation of SAMs without having to isolate the oxidatively unstable free thiols. Moreover, directidsorption, without exogenous base, of the thioacetyl-terminated oligomers can be accomplished to generate gold surface-bound thiolates. However, in the non-base-promoted adsorptions, higher concentrations of the thioaietyl groups, relative to that of thiol groups, are required to achieve monolayer coverage in a given interval. A thiol-teinninated phenylene-ethynylene system was shown to have a tilt angle of the long molecular axis of <20o from the normal to the substrate surface. These aromatic o-ro-dithiol-derived monolayers provide the basis for studies leading to the design of molecular wires capable of bridging proximate

Journal ArticleDOI
TL;DR: Data indicate that preservation of muscle mass and prevention of sarcopenia can help prevent the decrease in metabolic rate in the elderly.
Abstract: Advancing adult age is associated with profound changes in body composition, the principal component of which is a decrease in skeletal muscle mass. This age-related loss in skeletal muscle has been referred to as sarcopenia. Age-related reduction in muscle is a direct cause of the age-related decrease in muscle strength. Muscle mass (not function) appears to be the major determinant of the age- and sex-related differences in strength. This relationship is independent of muscle location (upper vs lower extremities) and function (extension vs flexion). Reduced muscle strength in the elderly is a major cause for their increased prevalence of disability. With advancing age and extremely low activity levels seen in the very old, muscle strength is a critical component of walking ability. The high prevalence of falls among the institutionalized elderly may be a consequence of their lower muscle strength. Daily energy expenditure declines progressively throughout adult life. In sedentary individuals, the main determinant of energy expenditure is fat-free mass, which declines by about 15% between the third and eighth decade of life, contributing to a lower basal metabolic rate in the elderly. Data indicate that preservation of muscle mass and prevention of sarcopenia can help prevent the decrease in metabolic rate. In addition to its role in energy metabolism, skeletal muscle and its age-related decline may contribute to such age-associated changes as reduction in bone density, insulin sensitivity, and aerobic capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Book ChapterDOI
01 Jan 1995

Book
14 Aug 1995
TL;DR: This chapter explains the basics of neuroscience and artificial neuron models graphs algorithms and applications of neural networks approach to solving hard problems.
Abstract: Part 1 Fundamentals: basics of neuroscience and artificial neuron models graphs algorithms. Part 2 Feedforward networks: perceptrons and LMS algorithm complexity of learning using feedforward networks adaptive structure networks. Part 3 Recurrent networks: symmetric and asymmetric recurrent network competitive learning and self-organizing networks. Part 4 Applications of neural networks: neural networks approach to solving hard problems.

Journal ArticleDOI
TL;DR: In this paper, leachate and humic and fulvic acid fractions of dissolved organic matter (DOM) released from senescent littoral aquatic plants were exposed to varying spectra of ultraviolet radiation as well as natural UV of sunlight over different periods of time.
Abstract: Whole leachate and humic and fulvic acid fractions of dissolved organic matter (DOM) released from senescent littoral aquatic plants were exposed to varying spectra of ultraviolet radiation as well as natural UV of sunlight over different periods of time. Examination of the DOM by solid-state 13C nuclear magnetic resonance and pyrolytic gas chromatography-mass spectrometry before and after photolysis revealed only subtle changes to the bulk DOM. However, the DOM exposed to natural UV radiation showed immediate stimulation of and sustained bacterial growth. Chemical analyses by high performance liquid chromatography (HPLC) of the small organic fractions generated by photolysis of humic substances showed marked, pro- ’ gressively increasing release of numerous small fatty acids, particularly acetic, formic, citric, pyruvic, and levulinic, among others. Use of radiolabeled humic substances demonstrated that these small compounds photolyzed from the humic substances were readily metabolized by the bacteria.

Book ChapterDOI
01 Apr 1995
TL;DR: In this paper, the authors focus on identifying important specific properties associated with the asymptotic behavior of smooth dynamical systems, including growth of the numbers of orbits of various kinds and complexity of orbit families, types of recurrence, and statistical behavior of orbits.
Abstract: In this chapter we will embark upon the task of systematically identifying important specific phenomena associated with the asymptotic behavior of smooth dynamical systems We will build upon the results of our survey of specific examples in Chapter 1 as well as on the insights gained from the general structural approach outlined and illustrated in Chapter 2 Most of the properties discussed in the present chapter are in fact topological invariants and can be defined for broad classes of topological dynamical systems, including symbolic ones The predominance of topological invariants fits well with the picture that emerges from the considerations of Sections 21, 23, 24, and 26 The considerations of the previous chapter make it very plausible that smooth dynamical systems are virtually never differentiably stable and can only rarely be classified locally up to smooth conjugacy In contrast, structural and the related topological stability seem to be fairly widespread phenomena We will consider three broad classes of asymptotic invariants: (i) growth of the numbers of orbits of various kinds and of the complexity of orbit families, (ii) types of recurrence, and (iii) asymptotic distribution and statistical behavior of orbits The first two classes are of a purely topological nature; they are discussed in the present chapter The last class is naturally related to ergodic theory and hence we will provide an introduction to key aspects of that subject This will require some space so we put that material into a separate chapter The two chapters are intimately connected

Journal ArticleDOI
TL;DR: The phylogenetic relationships and divergence times of 39 drosophilid species were studied by using the coding region of the Adh gene to show that Scaptomyza experienced a rapid morphological evolution and many of the D. repleta group species studied here have two functional Adh genes, and these duplicated genes can be explained by two duplication events.
Abstract: The phylogenetic relationships and divergence times of 39 drosophilid species were studied by using the coding region of the Adh gene. Four genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and Sophophora--were included. After conducting statistical analyses of the nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila as the outgroup. The phylogenetic tree obtained showed that the first major division of drosophilid species occurs between subgenus Sophophora (genus Drosophila) and the group including subgenera Drosophila and Engiscaptomyza plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then divided into D. willistoni and the clade of D. obscura and D. melanogaster species groups. In the other major drosophilid group, Zaprionus first separates from the other species, and then D. immigrans leaves the remaining group of species. This remaining group then splits into the D. repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila, Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups is monophyletic. The splitting of subgenera Drosophila and Sophophora apparently occurred about 40 Mya, whereas the D. repleta group and the Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya, suggesting that Scaptomyza experienced a rapid morphological evolution. The D. obscura and D. melanogaster groups apparently diverged about 25 Mya. Many of the D. repleta group species studied here have two functional Adh genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two duplication events.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the role of the anonymity hypothesis in the deviation from perfect equilibrium in the ultimatum game and conclude that the punishment hypothesis explains much more of the deviation than does the anonymity.