cssi/SciSciGPT-SciSciNet huggingface dataset:
Opposing effects of glutamine and asparagine govern prion formation by intrinsically disordered proteins

Sequences rich in glutamine (Q) and asparagine (N) residues often fail to fold at the monomer level. This, coupled to their unusual hydrogen-bonding abilities, provides the driving force to switch between disordered monomers and amyloids. Such transitions govern processes as diverse as human protein-folding diseases, bacterial biofilm assembly, and the inheritance of yeast prions (protein-based genetic elements). A systematic survey of prion-forming domains suggested that Q and N residues have distinct effects on amyloid formation. Here, we use cell biological, biochemical, and computational techniques to compare Q/N-rich protein variants, replacing Ns with Qs and Qs with Ns. We find that the two residues have strong and opposing effects: N richness promotes assembly of benign self-templating amyloids; Q richness promotes formation of toxic nonamyloid conformers. Molecular simulations focusing on intrinsic folding differences between Qs and Ns suggest that their different behaviors are due to the enhanced turn-forming propensity of Ns over Qs.
Alternating linearization for structured regularization problems

We adapt the alternating linearization method for proximal decomposition to structured regularization problems, in particular, to the generalized lasso problems. The method is related to two well-known operator splitting methods, the Douglas-Rachford and the Peaceman-Rachford method, but it has descent properties with respect to the objective function. This is achieved by employing a special update test, which decides whether it is beneficial to make a Peaceman-Rachford step, any of the two possible Douglas-Rachford steps, or none. The convergence mechanism of the method is related to that of bundle methods of nonsmooth optimization. We also discuss implementation for very large problems, with the use of specialized algorithms and sparse data structures. Finally, we present numerical results for several synthetic and real-world examples, including a three-dimensional fused lasso problem, which illustrate the scalability, efficacy, and accuracy of the method.
Broadcast communication delay metric for the iPSC/2 and iPSC/860 hypercubes

When determining the granularity of a program to be executed in parallel, it is important to have valid information on the cost of communication for the system on which the program is to be run. Previous studies have measured the node-to-node communication performance on the Intel Hypercube systems. This work measures the performance of multicast communication on the Intel iPSC/2 and iPSC/860 hypercubes and derives equations modelling the cost of broadcast communication.
A concise total synthesis of the aglycone of the gilvocarcins

Abstract A brief and convergent synthesis of the aglycone of the gilvocarcins M and E (and formally V) involving, in the key step, a Pd-mediated intramolecular biaryl coupling, is reported.
Calcium-catalyzed Friedel–Crafts addition of 1-methylindole to activated cyclopropanes

Abstract The synthesis of γ-indolyl malonates was achieved through the addition of indoles to activated cyclopropanes. These Friedel–Crafts reactions were catalyzed by calcium bis(trifluoromethanesulfonimide), Ca(NTf 2 ) 2 . The addition proceeded with complete regioselectivity and in good to excellent yields. Optimization of the reaction conditions and investigation into the scope of the reaction with regard to substitution on cyclopropane are reported.
Chemistry and the universities in the seventeenth century

T he appointment of de Renault as Professor of Chemistry at the University of Louvain in 1685 reflected more than a century of debate in European-learned circles (1). The followers of the Swiss-German reformer Paracelsus (1493-1541) had seen in chemistry and alchemy a new foundation for learning (2). Paracelsus had burned the Canon of Avicenna publically in 1527 at Basel and his followers rejected the Aristotelian-Galenic tradition of the universities. They saw little value in disputations or the study of logic and they sought an alternative to the four elements in Natural Philosophy and their attendant humors in medicine. They scorned the reading of the books of the ancient philosophers and saw truth primarily in the two books of Divine Revelation, the Bible and the Book of Creation or Nature.
Measuring the Income Generating Potential of Land in Rural Mexico

This paper measures the potential of land to generate income and establishes the contexts under which access to land can reduce poverty. Using Mexican household data, we apply nonparametric regression methods to estimate and graphically explore the relationship between land and welfare. Results suggest that the marginal value of land depends on both the complementary and contextual assets of the poor.
How to value a life

The tradeoff between money and small risks of death is the value of statistical life (VSL), which has become the standard for assessing the benefits of risk and environmental regulations. Labor market estimates of the VSL average about $7 million. This valuation amount rises with age and then declines, closely tracking the pattern of consumption over the life cycle. The VSL for those at age 60 is higher than for people in their 20s. Application of this methodology to assess the mortality costs to smokers indicates a personal mortality cost on the order of $200 per pack for men and $100 for women using a 3% discount rate, but based on smokers’ rates of time preference the costs are reduced by about an order of magnitude.
On the Local Smoothness of Solutions of the Navier-Stokes Equations

We consider the Cauchy problem for incompressible Navier–Stokes equations $$u_t + u\nabla_xu - \Delta_xu + \nabla_xp = 0,\; {\text{div}}\,u = 0\;{\text{in}}\;\mathbb{R}^d \times \mathbb{R}^ +$$ with initial data in $$L^d (\mathbb{R}^d )$$ , and study in some detail the smoothing effect of the equation. We prove that for T < ∞ and for any positive integers n and m we have $$t^{m + n/2} D_t^m D_x^n u \in L^{d + 2} (\mathbb{R}^d \times (0,T))$$ , as long as $$||u||_{L_{x,t}^{d + 2} (R^d \times (0,T))}$$ stays finite.
Studies of the wall shear stress in a turbulent pulsating pipe flow

Measurements are presented of the time variation of the wall shear stress caused by the imposition of a sinusoidal oscillation on a turbulent pipe flow. The amplitude of the oscillation is small enough that a linear response is obtained and the dimensionless frequency, ω+ = ων/u*2, is large compared with that studied by most previous investigators. The most striking feature of the results is a relaxation effect, similar to that observed for flow over a wavy surface, whereby the phase angle characterizing the temporal variation of the wall shear stress undergoes a sharp change over a rather narrow range of ω+. At ω+ larger than the median frequency of the turbulence there appears to be an interaction between the imposed flow oscillation and the turbulence fluctuations in the viscous sublayer, which is not described by present theories of turbulence.
Reserve Requirement Impacts of Large-Scale Integration of Wind, Solar, and Ocean Wave Power Generation

Many sources of renewable energy, including solar, wind, and ocean wave, offer significant advantages such as no fuel costs and no emissions from generation. However, in most cases these renewable power sources are variable and nondispatchable. The utility grid is already able to accommodate the variability of the load and some additional variability introduced by sources such as wind. However, at high penetration levels, the variability of renewable power sources can severely impact the utility reserve requirements. This paper presents an analysis of the interaction between the variability characteristics of the utility load, wind power generation, solar power generation, and ocean wave power generation. The results show that a diversified variable renewable energy mix can reduce the utility reserve requirement and help reduce the effects of variability.
Karl Popper and Economic Methodology: A New Look

Discussions of Karl Popper's falsificationist philosophy of science appear regularly in the recent literature on economic methodology. In this literature, there seem to be two fundamental points of agreement about Popper. First, most economists take Popper's falsificationist method of bold conjecture and severe test to be the correct characterization of scientific conduct in the physical sciences. Second, most economists admit that economic theory fails miserably when judged by these same falsificationist standards. As Latsis (1976, p. 8) states, “the development of economic analysis would look a dismal affair through falsificationist spectacles.”
Inositol polyphosphates, diphosphoinositol polyphosphates and phosphatidylinositol polyphosphate lipids: Structure, synthesis, and development of probes for studying biological activity

Covering: 2006 up to June 2010, but also including representative examples of prior work Polyphosphorylated myo-inositol compounds, including the inositol polyphosphates (InsPs), diphosphoinositol polyphosphates (PP-InsPs), and phosphatidylinositol polyphosphates (PIPns), represent key biomolecules that regulate a litany of critical biological processes. These compounds exist with myriad combinations of phosphorylation patterns, resulting in a complex network of interconverting signaling molecules that control different events. Due to the significance and intricate nature of this molecular family, the elucidation of biological roles has elicited substantial interest in both the biochemical and chemical communities. Within this broad effort, strategies employing chemical synthesis for the production of both natural products and chemically modified structures have proven advantageous for determining activities. Herein, we will discuss recent advancements in these efforts, including (i) a brief overview of structure and biological activity, (ii) current methods for the chemical synthesis of phosphorylated myo-inositols, (iii) strategies for the design of biologically active probe structures, and (iv) case studies in which synthetic probes have been applied to characterize biological properties.
Synthesis of the first diarsadigalletane

Abstract The diarsadigalletane [ 1 BuGaAsC 6 H 3 (CH 2 NMe 2 ) 2 ] ( 1 ) has been prepared by treatment of [ 1 BuGaCl 2 ] 2 with Li 2 AsC 6 H 3 (CH 2 NMe 2 ) 2 in Et 2 O solution. One of the Me 2 N groups of each (Me 2 NCH 2 ) 2 C 6 H 3 ring is coordinated to each of the gallium atoms in the As 2 Ga 2 ring. Compound 1 is air and moisture stable.
User-Adaptable Comfort Control for HVAC Systems

This paper describes a new approach to the control of heating, ventilating and air-conditioning(HVAC) system. In the conventional method for controlling HVAC systems, the occupant adjusts the reference input whenever the condition are uncomfortable. The reference input must be periodically adjusted because the controlled variable does not accurately reflect the comfort of the specific occupant. The fundamental concept of the approach described in this paper is that the controller learns to predict the actual thermal sensation of the specific use by tuning parameters of a model of thermal sensation. The parameters are adjusted with respect to the actual thermal sensation ratings of the specific occupant so that with time the model accurately reflects the comfort of the specific occupant. The stability of the controller is maintained by utilizing a priori information about the parameters of the model of thermal sensation. The method is implemented on a residential heat pump air conditioner. Experiments using human subjects verify the usefulness and feasibility of the method.
Repeated labeling using multiple noisy labelers

This paper addresses the repeated acquisition of labels for data items when the labeling is imperfect. We examine the improvement (or lack thereof) in data quality via repeated labeling, and focus especially on the improvement of training labels for supervised induction of predictive models. With the outsourcing of small tasks becoming easier, for example via Amazon's Mechanical Turk, it often is possible to obtain less-than-expert labeling at low cost. With low-cost labeling, preparing the unlabeled part of the data can become considerably more expensive than labeling. We present repeated-labeling strategies of increasing complexity, and show several main results. (i) Repeated-labeling can improve label quality and model quality, but not always. (ii) When labels are noisy, repeated labeling can be preferable to single labeling even in the traditional setting where labels are not particularly cheap. (iii) As soon as the cost of processing the unlabeled data is not free, even the simple strategy of labeling everything multiple times can give considerable advantage. (iv) Repeatedly labeling a carefully chosen set of points is generally preferable, and we present a set of robust techniques that combine different notions of uncertainty to select data points for which quality should be improved. The bottom line: the results show clearly that when labeling is not perfect, selective acquisition of multiple labels is a strategy that data miners should have in their repertoire; for certain label-quality/cost regimes, the benefit is substantial.
Parents' investments and education returns

Abstract This paper analyses the relation between parents’ earnings and their children's education. In a context of perfect altruism, the model describes parents’ decisions on how much to consume and how much to invest in their children's education. The model predicts that returns on education in terms of wages should be linear. Using this model in a competitive economy, we show how the outcome depends on government subsidies or taxes on education. The usual tradeoff equality-efficiency arises in this context. Finally, the model provides some insights into the relation between education and productivity.
Boundary Data Maps for Schrödinger Operators on a Compact Interval

We provide a systematic study of boundary data maps, that is, 2 £ 2 matrix-valued Dirichlet-to-Neumann and more generally, Robin-to-Robin maps, associated with one-dimensional Schr¨ odinger operators on a compact interval (0;R) with separated boundary conditions at 0 and R. Most of our results are formulated in the non-self-adjoint context. Our principal results include explicit representations of these boundary data maps in terms of the resolvent of the underlying Schr¨ odinger operator and the associated boundary trace maps, Krein-type resolvent formulas relating Schr¨ odinger operators corresponding to different (sepa- rated) boundary conditions, and a derivation of the Herglotz property of boundary data maps (up to right multiplication by an appropriate diagonal matrix) in the special self-adjoint case.
Incentives and Penalties Related to Earnings Overstatements that Violate GAAP

This paper investigates the incentives and the penalties related to earnings overstatements primarily in firms that are subject to accounting enforcement actions by the Securities and Exchange Commission (SEC). I find (1) that managers in treatment firms are more likely to sell their holdings and exercise stock appreciation rights in the period when earnings are overstated than are managers in control firms, and (2) that the sales occur at inflated prices. I do not find evidence that earnings overstatement in these firms is motivated by concerns about debt covenant violations or the cost of external financing. The evidence suggests that the monitoring of managers' trading behavior can be informative about the likelihood of earnings overstatement. Many economists believe that insider trading is an efficient method of compensating managers for their efforts. These economists argue that reputation losses would preclude managers from making profitable trades before periods of poor corporate performance. Conse...
A scalable Nenitzescu synthesis of 2‐methyl‐4‐(trifluoromethyl)‐1H‐indole‐5‐carbonitrile

2-Methyl-4-(trifluoromethyl)-1H-indole-5-carbonitrile is a key intermediate in the synthesis of selective androgen receptor modulators discovered in these laboratories. A practical and convergent synthesis of the title compound starting from 4-nitro-3-(trifluoromethyl)phenol and tert-butyl acetoacetate was developed, including a telescoped procedure for synthesis (without isolation) and Nenitzescu reaction of 2-trifluoromethyl-1,4-benzoquinone. Conversion of the known Nenitzescu indole product to a novel triflate intermediate followed by palladium-catalyzed cyanation afforded a penultimate carbonitrile. Removal of the C-3 tert-butyl ester group on the indole through a decarboxylative pathway completed the synthesis of the title compound in six steps (27% overall yield) from 4-nitro-3-(trifluoromethyl)phenol (five steps, 37% overall yield from tert-butyl acetoacetate). J. Heterocyclic Chem., (2011).
Higher-order vector finite elements for tetrahedral cells

Edge-based vector finite elements are widely used for two-dimensional (2-D) and three-dimensional (3-D) electromagnetic modeling. This paper seeks to extend these low-order elements to higher orders to improve the accuracy of numerical solutions. These elements have relaxed normal-component continuity to prohibit spurious modes, and also satisfy Nedelec's constraints to eliminate unnecessary degrees of freedom while remaining entirely local in character. Element matrix derivations are given for the first two vector finite element sets. Also, results of the application of these basis functions to cavity resonators demonstrate the superiority of the higher-order elements.
Goldberger-Treiman constants of dynamical near-Goldstone modes

Within the framework of a model for the quantum-chromodynamic vacuum, a collision-theory argument is used to assess the magnitudes of the Goldberger-Treiman constants of dynamical near-Goldstone modes. The values so estimated for f/sub ..pi../ and f/sub K/ are in fair agreement with observation.
The Fuzzball proposal for black holes: An Elementary review

We give an elementary review of black holes in string theory. We discuss BPS holes, the microscopic computation of entropy and the `fuzzball' picture of the black hole interior suggested by microstates of the 2-charge system.
Tiling a Polygon with Two Kinds of Rectangles

We fix two rectangles with integer dimensions. We give a quadratic time algorithm which, given a polygon F as input, produces a tiling of F with translated copies of our rectangles (or indicates that there is no tiling). Moreover, we prove that any pair of tilings can be linked by a sequence of local transformations of tilings, called flips. This study is based on the use of Conway’s tiling groups and extends the results of Kenyon and Kenyon (limited to the case when each rectangle has a side of length 1).
Exact solutions of model hamiltonian problems with effective interactions

Abstract We verify with soluble models that the effective-hamiltonian approach of Lee and Suzuki can be used to obtain all the exact eigenvalues of the full hamiltonian. We propose a new iteration scheme to obtain the effective hamiltonian and demonstrate its convergence properties.
Signature Theory in Holographic Algorithms

In the theory of holographic algorithms proposed by Valiant, computation is expressed and processed in terms of signatures. We substantially develop the signature theory in holographic algorithms. This theory is developed in terms of d-realizability and d-admissibility. For the class of 2-realizable signatures we prove a Birkhoff-type theorem which determines this class. It gives a complete structural understanding of the relationship between 2-realizability and 2-admissibility. This is followed by characterization theorems for 1-realizability and 1-admissibility. Finally, using this theory of general (i.e., unsymmetric) signatures we give additional counting problems solvable in polynomial time by holographic algorithms.
Synthesis and Friction Behavior of Chemically Vapor Deposited Composite Coatings Containing Discrete TiN and MoS2 Phases

Composite coatings containing discrete crystalline phases of TiN and MoS{sub 2} were deposited on Si, graphite, and Ti-6Al-4V alloy substrates by simultaneous chemical vapor deposition. MoF{sub 6} and H{sub 2}S were utilized as the precursors for MoS{sub 2} formation, while Ti((CH{sub 3}){sub 2}N){sub 4} and NH{sub 3} were used for TiN deposition. The composition and microstructure of the coatings were investigated by X-ray diffraction, Auger electron spectroscopy, and transmission electron microscopy. The molar ratios of TiN and MoS{sub 2} in the composite microstructure could be controlled by adjusting the MoF{sub 6} concentration in the reagent mixture. Encouraging friction and wear characteristics against silicon nitride were obtained for a composite coating which was rich in MoS{sub 2} at the coating surface, with TiN as the major phase near the substrate interface. Friction coefficients at room temperature in air were typically in the range of 0.07 to 0.3. The friction coefficients remained comparable at 573 K, but increased to 0.7 to 1.0 at 673 K. A friction coefficient value of {approximately}0.3 was, however, obtained from a composite coating tested at 973 K.
International Trade and Competitiveness of Lake Victoria Fillets in the EU

Given the importance of EU demand for chilled fish fillets to the exporting sectors in Tanzania and Uganda, this study estimated the EUs import demand for fillets by country of origin to assess the competitiveness of exporters. Results imply that prices in Tanzania and Uganda had an insignificant impact on total imports expenditures in the EU. Conditional and unconditional cross-price effects indicated that exports from Lake Victoria did not compete with exports from other suppliers, such as Iceland, Norway and ROW. Import demand forecasts showed that market share in the EU should remain relatively unchanged given the trend in prices.
Excess liquidity and the foreign currency constraint: the case of monetary management in Guyana

This article examines why commercial banks in Guyana demand nonremunerated excess reserves, a phenomenon that became even more widespread after financial liberalization. Despite the removal of capital controls, banks do not invest all excess reserves in a safe foreign asset because the central bank maintains an unofficial foreign currency constraint by accumulating international reserves. The findings suggest that commercial banks do not demand excess reserves for precautionary purpose–which is the conclusion of several other studies–but rather because of the maintained constraint. The estimated sterilization coefficient is consistent with the hypothesis of an enforced constraint. The results, moreover, suggest an alternative way of looking at the monetary transmission mechanism in developing countries. The central bank maintains price and exchange rate stability through the accumulation of foreign reserves.
Ethical Theory and Stakeholder-Related Decisions: The Role of Stakeholder Culture

We use convergent elements of major ethical theories to create a typology of corporate stakeholder cultures–the aspects of organizational culture consisting of the beliefs, values, and practices that have evolved for solving problems and otherwise managing stakeholder relationships. We describe five stakeholder cultures–agency, corporate egoist, instrumentalist, moralist, and altruist–and explain how these cultures lie on a continuum, ranging from individually self-interested (agency culture) to fully other-regarding (altruist culture). We demonstrate the utility of our framework by showing how it can refine stakeholder salience theory.
Entrainment Limits in Heat Pipes

The present work explores the physical basis for the entrainment limit in heat pipes and attempts to develop adequate quantitative criteria for the limit. Analogy is emphasized here between the entrainment phenomenon in heat pipes and the flooding phenomenon in countercurrent vapor-liquid flow systems. The maximum operating heat-transfer rates for various heat pipes due to entrainment limitation are established semiempirically by way of modifying existing flooding correlations. While the present results are successful in correlating the limited experimental data available, further experimental studies are needed in assessing the validity of the established criteria.
The continuous behavior of the numéraire portfolio under small changes in information structure, probabilistic views and investment constraints

The numeraire portfolio in a financial market is the unique positive wealth process that makes all other nonnegative wealth processes, when deflated by it, supermartingales. The numeraire portfolio depends on market characteristics, which include: (a) the information flow available to acting agents, given by a filtration; (b) the statistical evolution of the asset prices and, more generally, the states of nature, given by a probability measure; and (c) possible restrictions that acting agents might be facing on available investment strategies, modeled by a constraint set. In a financial market with continuous-path asset prices, we establish the stable behavior of the numeraire portfolio when each of the aforementioned market parameters is changed in an infinitesimal way.
A collaborative approach to in-place sensor calibration

Numerous factors contribute to errors in sensor measurements. In order to be useful, any sensor device must be calibrated to adjust its accuracy against the expected measurement scale. In large-scale sensor networks, calibration will be an exceptionally difficult task since sensor nodes are often not easily accessible and manual device-by-device calibration is intractable. In this paper, we present a two-phase post-deployment calibration technique for large-scale, dense sensor deployments. In its first phase, the algorithm derives relative calibration relationships between pairs of co-located sensors, while in the second phase, it maximizes the consistency of the pair-wise calibration functions among groups of sensor nodes. The key idea in the first phase is to use temporal correlation of signals received at neighboring sensors when the signals are highly correlated (i.e. sensors are observing the same phenomenon) to derive the function relating their bias in amplitude. We formulate the second phase as an optimization problem and present an algorithm suitable for localized implementation. We evaluate the performance of the first phase of the algorithm using empirical and simulated data.
Lattice Dynamics and Ionicity in the High-Temperature Superconductors

Using a non-empirical ionic model, we find harmonically unstable, double well potential surfaces for both La 2 CuO 4 and YBa 2 Cu 3 O 7 which may be related to the high temperature superconductivity. We have applied the Potential Induced Breathing (PIB) Model to La 2 CuO 4 and YBa 2 Cu 3 O 7 and find that the ionic description gives semiquantitative agreement with structural and vibrational observations. Furthermore, comparison with self-consistent linearized augmented plane wave [1] (LAPW) calculations shows that ionic contributions to the bonding and lattice dynamics of oxide superconductors are large. For La 2 CuO 4 we find that an ionic description predicts the observed tetragonal to orthorhombic distortion, predicts a lower symmetry ground state, and predicts a stable oxygen breathing mode. We find harmonically unstable phonon branches that we relate to phase transitions. Unstable (anharmonic) modes will couple via ionic forces to the charge density in the metallic planes. This ionic coupling has not been included in previous lattice dynamics calculations. For YBa 2 Cu 3 O 7 we find similar unstable phonon branches that involve oxygen motions perpendicular to the Cu-O bonds. We find the crystalline charge density is best approximated by overlapping ions if Cu and O ions of charge +1.6 and -1.8, respectively, are used.
Motives for sharing in social networks

What motivates people in rural villages to share? We rst elicit a baseline level of sharing using a standard, anonymous dictator game. Then using variants of the dictator game that allow for either revealing the dictator’s identity or allowing the dictator to choose the recipient, we attribute variation in sharing to three dierent motives. The rst of these, directed altruism, is related to preferences, while the remaining two are incentive-related (sanctions and reciprocity). We observe high average levels of sharing in our baseline treatment, while variation across individuals depends importantly on the incentive-related motives. Finally, variation in measured reciprocity within the experiment predicts observed ‘real-world’ gift-giving, while other motives measured in the experiment do not predict behavior outside the experiment.
Computation of Superpotentials for D-Branes

We present a general method for the computation of tree-level superpotentials for the world-volume theory of B-type D-branes. This includes quiver gauge theories in the case that the D-brane is marginally stable. The technique involves analyzing the A ∞-structure inherent in the derived category of coherent sheaves. This effectively gives a practical method of computing correlation functions in holomorphic Chern–Simons theory. As an example, we give a more rigorous proof of previous results concerning 3-branes on certain singularities including conifolds. We also provide a new example.
Governance and Hyper-corruption in Resource-rich African Countries

Abstract Official corruption is frequently associated with the abundance of valuable extractive resources. This article reviews the worst cases of ‘resource curse’ in Africa—Angola, Republic of Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, and Nigeria—in light of the most recent developments. Despite its systematic association with public corruption, however, mineral wealth is neither a necessary nor a sufficient condition. Corruption is widespread in resource-poor countries as well—in Africa and elsewhere—and some resource-rich African countries such as Botswana have a record of good economic performance and high public integrity, suggesting specific ways in which transparency and accountability for the use of mineral resources can be encouraged and corruption correspondingly reduced. Because corruption in resource-rich African countries is heavily influenced by external interests, particularly the multinational extractive industries, recent initiatives by the United States and the inter...
Persistent wakefields associated with waveguide damping of higher order modes

By means of an analytic model and numerical simulations we demonstrate that the wake of a waveguide damped cavity contains a persistent component which decays as t/sup -3/2/ and thus is dominant at sufficiently large values of t. Because there are scenarios for which the effect gives rise to unacceptable beam instability, it cannot be ignored, but it seems likely that such an outcome can be avoided with proper design. >
Factors That Influence Elementary Teachers Use of Computers

The purpose of this quantitative study was to examine the ways elementary teachers use computer technology for instructional purposes and the factors that influence their use of computers. The population consisted of recent graduates from the elementary teacher preparation program at a mid-Atlantic university. Data were gathered using a survey instrument. The instrument addressed the four factors that support teachers’ use of computers: access and availability, preparation and training, leadership, and time. Descriptive and inferential statistics were employed in this study. The response rate was 89 percent. The findings indicated that 84 percent of the teachers felt either well or very well prepared to integrate technology into curriculum, and that they were able to overcome the typical barriers to computer use in elementary classrooms. The teachers overwhelmingly indicated that computers have considerable potential for allowing students to discover or construct ideas for themselves and supported constructivist pedagogies when referring to computer use in elementary classrooms. Teacher preparation, teacher philosophy and grade level were identified as influential factors in the use of computers by the elementary teachers and the elementary students.
Dimensions of Human Development

Summary. — If human development is ‘‘multidimensional’’ then perhaps we need to discuss what we mean by multidimensional: what is a dimension, and what are the multiple dimensions of interest? This paper develops an account of dimensions of human development, and shows its usefulness and its limitations—both in general and in relation to Amartya Sen’s capability approach. The second half of the paper surveys other major ‘‘lists’’ of dimensions that have been published in poverty studies, crosscultural psychology, moral philosophy, quality of life indicators, participatory development, and basic needs, and compares and contrasts them with the account sketched here. 2002 Elsevier Science Ltd. All rights reserved.
Microporous Porphyrin Solids

Metalloporphyrins are exceedingly useful building blocks for the design and synthesis of molecularly based solids. The use of hydrogen bonding or metal ion coordination provides a wide range of framework solids. Using various polyfunctionalized porphyrins, we have created porous solids that are thermally robust and that retain their internal porosity upon loss of solvates. Their pore dimensions are comparable to zeolites, and they show shape and size selectivity in sorption of guest molecules and in epoxidation of alkenes.
Proportion dominance: The generality and variability of favoring relative savings over absolute savings☆

Four studies probe Ps sensitivity to absolute and relative savings. In three studies, Ps read scenarios forcing a tradeoff of saving more lives (230 vs. 225) vs. saving a larger proportion of a population (225 ‚ 230 = 75% vs. 230 ‚ 920 = 25%). Ps preferences were driven by both absolute and relative savings. Maximizing relative savings, called ‘‘proportion dominance’’ (PD), at the expense of absolute savings is non-normative, and most participants concur with this argument upon reflection (Studies 2 and 3). PD is related to individual differences, such that people scored as ‘‘rational’’ thinkers exhibited less PD than people scored as ‘‘experiential’’ thinkers (Studies 1 and 3). Finally, a fourth study extends these results, finding proportion dominance in other domains using a different paradigm. These four studies demonstrate both the generality (across domains and paradigms) and the variability (inter- and intraindividual) of proportion dominance.
Segmentation and optimization of programs from cyclic structure analysis

Modelling of computer programs by directed graphs, where the vertices represent the computational tasks and the arcs show the flow of control, has been used for optimization purposes, parallel processing evaluation, and segmentation. All these studies are mainly based on the fact that a high proportion of the execution time of a program is spent in loops. Although the cyclic structure of programs can be theoretically complex, it has been observed that the nestedness is seldom very deep. Thus if one wants to optimize programs written in a high-level language, the detection of cycles by the compiler and its use in an optimization phase may yield a definite improvement in execution time without having to pay too heavily for excess compiling time. In this paper we show how a compiler could make use of an efficient cycle detection algorithm to model the embeddedness of cycles by an acyclic directed graph. The latter can then be used for packing purposes in case of a paging or "cache" memory system as well as for predicting the expected number of executions of a given statement for optimization purposes.
Turkish Immigrants' Hopes and Fears around Return Migration

This paper seeks to understand the process by which immigrants decide whether or not to return to their home countries. It aims to analyse the potential for return migration rather than the actual migration process. Empirically, it is based on the narratives of 30 Turkish immigrants living in the United States. The findings indicate that: (1) multiple controllable and uncontrollable, micro- and macro-level factors in both the home and the host countries interact over time to tip the scales towards – or away from – return migration; and (2) most immigrants live in a perpetual state of ambivalence about whether or not to engage in return migration. These findings are discussed, and implications are presented for both practice and policy.
Is fairness used instrumentally? Evidence from sequential bargaining

The equal split is a widely observed outcome in experimental studies of two-person bargaining. Until now only joint hypotheses that combine assumptions about preferences with equilibrium concepts have been used to explain the origin of the equal split. This paper reports an experiment that controls for the preferences of subjects and therefore sheds light on the social orientation of those proposers who make fair offers. The data suggest that fair offers are due to players with fair social orientations, but egoists use fairness instrumentally by increasing offers when they anticipate low offers will be rejected. When responding to offers, rather than principled fairmen defending the equal split, the data suggest that competitive individuals are responsible for most rejections.
A Common Multi-agent Testbed for Diverse Seamless Personal Information Networking Applications

The paper describes the design and implementation of a unique cooperative agents testbed intended for diverse applications in seamless personal information networking. The real-world SPINTM1 testbed is aimed at two applications, namely seamless messaging and intelligent network management. Both are agent-driven and share agent behaviours. The messaging agents rely on the network management device diagnostic agents for input. The first generation of Seamless MessagingTM is described in detail. It is user-centric and assumes heterogeneous communication environments intended to support today's nomadic users. A prototype is introduced for the management of messages across distributed information networks. Its aim is to intercept, filter, interpret, and deliver multi-modal messages be they voice, fax, video and/or e-mail messages. A user's Personal Communication AgentTM (PCA) is charged with delivering messages to the recipient regardless of their target messaging device be it a telephone, a pager, a desktop, a wireless laptop or a wireless phone. PCAs classify and act on incoming messages based on their content. A Secretary AgentTM routes and tailors urgent messages appropriately to the Device Manager AgentTM which delivers the message to a device that the user may be roaming or active on. What makes Seamless Messaging unique is its approach to treating a message in a universal manner, its ability to mediate between different messaging environments and devices, and its capability of tracking and finding users.
Soil Moisture Feedbacks on Convection Triggers: The Role of Soil-Plant Hydrodynamics

Abstract The linkages between soil moisture dynamics and convection triggers, defined here as the first crossing between the boundary layer height (hBL) and lifting condensation level (hLCL), are complicated by a large number of interacting processes occurring over a wide range of space and time scales. To progress on this problem, a soil–plant hydrodynamics model was coupled to a simplified ABL budget to explore the feedback of soil moisture on convection triggers. The soil–plant hydraulics formulation accounted mechanistically for features such as root water uptake, root water redistribution, and midday stomatal closure, all known to affect diurnal cycles of surface fluxes and, consequently, ABL growth. The ABL model considered the convective boundary layer as a slab with a discontinuity at the inversion layer. The model was parameterized using the wealth of data already collected for a maturing Loblolly pine plantation situated in the southeastern United States. A 30-day dry-down simulation was used to...
Feedback linear induction accelerator using fusion reactor exhaust plasma

Design of the feedback linac is centered on using the exhaust fusion reactor plasma at sustained pumping velocity to act as the moving core for the linac continuum, interacting with the controlled pulsing current producing the exciting magnetic field. The continuous interaction will generate perturbations in the imposed magnetic field with subsequent formation of regional and intentional boundary layer separation. An electric accelerating field will be produced by the magnetofluid interaction with the effective dominant role along the downstream region of the divertor channel, over which the accelerating field has an effect. The output accelerated plasma could then be recycled for reacceleration or to serve as a renewal medium for the acceleration core. It is predicted that the new design concept of the feedback linac will have a significant impact on the acceleration of heavy ion beams in fusion research as well as on new operational design for linear induction accelerators. >
Finite-frequency sensitivity kernels for boundary topography perturbations

SUMMARY We use the Born approximation in conjunction with body-wave ray theory to derive a readily
Unmanned Aerial Vehicles: Autonomous Control Challenges, A Researcher’s Perspective

AFRL is pressing ahead with development of truly autonomous UAV control systems. As we go from systems where the human is the pilot, through systems where the human is the operator, to systems where the human is the supervisor; with the ultimate goal simply to have the human as customer of UAV ops, we are running into numerous challenges. Yes, we face the typical technological questions of “What types of human tasks can we replace with on-board algorithms?” and “How big of a processor is required on-board to do this?”. What are usually not asked are other questions, maybe not technically exciting, but with enormous practical impact: “How can we affordably add more code to already costly flight critical s oftware programs?” “How do I flight certify a system that has non-deterministic attributes?” “What is the impact of implementing distributed, coordinated, info-centric control systems that now have flight critical data links susceptible to electronic and information warfare?” “How do I convince the FAA, and foreign governments, that it’s safe to let autonomous vehicles roam the skies?” These, and other questions, have just as great, if not greater, impact on systems development as the raw autonomous technology itself. This paper examines some of these challenges, how current AFRL research is addressing them, and points the way to future research that will allow truly autonomous operations.
The Janus nature of heme

Covering: 2003 to present The role of heme in enzymes, globins, and cytochromes has been known for some time and our understanding on how the heme participates in the various functional aspects of these proteins is fairly well advanced. More recent work has uncovered the role of heme as a regulatory molecule and as a gas sensor. Some of the newer advances in the role heme plays in enzyme catalyzed redox transformations and regulation/sensing will be described in this Highlight.
Markets, trade and the role of institutions in African development

This paper focuses on the interdependence between international trade and institutional reform and suggests that the trade barriers erected by advanced countries on the agricultural exports of poor countries, in particular sub-Saharan agriculture serve as an impediment to economic growth and development. Drawing upon recent literature, the suggestion is that trade barriers inhibit institutional reform that is a major factor affecting economic growth. An empirical analysis of trade reform and economic growth shows that sub-Saharan economies can reciprocate potential gains from increased trade, which are larger when an integration with world markets induces institutional reform.
The Reorientation of Transition Countries' Exports: Changes in Quantity, Quality and Variety

Exports from transition countries to market economies have increased considerably since the fall of socialism. The countries of Central and Eastern Europe have generally been more successful in this regard than the countries of the Commonwealth of Independent States. There are also considerable differences between countries within both the CEEC and the CIS, however. The following paper uses a variety of measures to determine the factors behind these cross-country differences.
Beneficial Effect of ortho-Methoxy Groups in the Asymmetric Ring Opening of meso Epoxides with Silicon Tetrachloride Catalyzed by Chiral ortho-Methoxyphenyldiazaphosphonamide Lewis Bases Response to the Communication by G. Buono et al.

The reported ability of chiral phosphonamide 1 to effect the enantioselective opening of meso epoxides with silicon tetrachloride has not withstood experimental verification by Denmark's group. Having reexamined the ring-opening of cyclooctene oxide, Denmark and co-workers found a serious discrepancy between their results (81-83 % recovery of the epoxide and an essentially racemic product) and those reported by Buono et al. (77 % yield and >99 % ee).
A Model of the “It” Products in Fashion

One of the characteristics of the fashion marketplace is the unpredictability and apparent randomness of fashion hits. Another one is the information asymmetry among consumers. In this paper, we consider fashion as a means consumers use to signal belonging to a higher social rank and propose an analytical model of fashion hits in the presence of competition and consumers who can coordinate on which product to use. We show that, consistent with the observed market phenomenon, in equilibrium, consumer coordination involves randomization between products chosen, i.e., in randomness of fashion hits. Analyzing optimal consumer choice, we find that whenever low-type consumer demand for a product is positive, a price increase results in a higher probability of high-type consumers choosing this product but lower low-type consumer demand. We also show that although high-type consumers may prefer higher prices that would lead to complete separation of the high-and the low-type consumers through product use, in equilibrium, firms always price as to attract positive demand from low-type consumers. The equilibrium price and profits turn out to be nonmonotonic in the low-type consumer valuation of being recognized as belonging to a higher social rank. Equilibrium profits first increase and then decrease in this valuation.
Characterization of unlabeled level planar trees

Consider a graph G with vertex set V in which each of the n vertices is assigned a number from the set {1,...,k} for some positive integer k. This assignment @f is a labeling if all k numbers are used. If @f does not assign adjacent vertices the same label, then @f forms a leveling that partitions V into k levels. If G has a planar drawing in which the y-coordinate of all vertices match their labels and edges are drawn strictly y-monotone, then G is level planar. In this paper, we consider the class of level trees that are level planar regardless of their labeling. We call such trees unlabeled level planar (ULP). Our contributions are three-fold. First, we describe which trees are ULP and provide linear-time level planar drawing algorithms for any labeling. Second, we characterize ULP trees in terms of forbidden subtrees so that any other tree must contain a subtree homeomorphic to one of these. Third, we provide a linear-time recognition algorithm for ULP trees.
A note on quantization in the presence of gravitational shock waves

We study the quantization of a free scalar field when the background metric satisfies Einstein's equations and develops gravitational shock waves.