cssi/SciSciGPT-SciSciNet huggingface dataset:
The Cost of Being Landlocked : Logistics Costs and Supply Chain Reliability

In the last two decades new emphasis has been given to the economic impact of geography, especially on the cost of being landlocked. From a development perspective, understanding the cost of being landlocked and its economic impact is critical, since one country of four in the world is landlocked (almost one out of three in Sub-Saharan Africa). Attempts to address the cost of being landlocked have mainly focused on regional and multilateral conventions aiming at ensuring freedom of transit, and on the development of regional transport infrastructure. The success of these measures has been limited, and many massive investments in infrastructure seem to have had a disappointing impact on landlocked economies. Although there may still be an infrastructure gap, this book, based on extensive data collection in several regions of the world, argues that logistics and trade services efficiency can be more important for landlocked countries than investing massively in infrastructure. Logistics have become increasingly complex and critical for firms' competitiveness, and a weakness in this field can badly hurt firms based in landlocked countries. This book proposes a revised approach to tackling the cost of being landlocked and a new analytical framework which uses a microeconomic approach to assess the trade and macroeconomic impacts of logistics. It takes into account recent findings on the importance of logistics chain uncertainty and inventory control in firms' performance. It argues that: (i) exporters and importers in landlocked developing countries face high logistics costs, which are highly detrimental to their competitiveness in world markets, (ii) high logistics costs depend on low logistics reliability and predictability, and (iii) low logistics reliability and predictability result mostly from rent-seeking and governance issues (prone to proliferate in low volume environments).
Construction of the K = 8 fractional superconformal algebras

Abstract We construct the K = 8 fractional superconformal algebras. There are two such extended Virasoro algebras, one of which was constructed earlier, involving a fractional spin (equivalently, conformal dimension) 6 5 current. The new algebra involves two additional fractional spin currents with spin 13 5 . Both algebras are non-local and satisfy non-abelian braiding relations. The construction of the algebras uses the isomorphism between the Z 8 parafermion theory and the tensor product of two tricritical Ising models. For the special value of the central charge c = 52 55 , corresponding to the eighth member of the unitary minimal series, the 13 5 currents of the new algebra decouple, while two spin 23 5 currents (level-2 current algebra descendants of the 13 5 currents) emerge. In addition, it is shown that the K = 8 algebra involving the spin 13 5 currents at central charge c = 12 5 is the appropriate algebra for the construction of the K = 8 (four-dimensional) fractional superstring.
CONFORMATIONAL ENERGY CALCULATIONS ON FIVE-MEMBERED RINGS IN PENTACOORDINATE PHOSPHORUS

Abstract It is shown in agreement with X-ray data that the square pyramid (SP) conformation of five-membered ring containing pentacoordinate phosphorus is stabilized relative to the corresponding trigonal bypyramid (TP) when the ring systems are unsaturated and contain highly electronegative heteroatoms directly attached to phosphorus. The primary cause of the stabilization is attributed to ring strain produced by differences in bond lengths which are inherent in the TP form for equatorial vs. apical bonds. For dioxaphospholene compounds examined, ring strain is estimated to be about 3–4 kcal/mol greater in the TP. This enhances the overall stability of the SP conformation relative to the TP form. As the electronegativity of the heteroring atoms is reduced, ring strain effects become less important and the TP appears as the more stable structure in line with structural evidence. The presence of mixed heteroring atoms directly attached to phosphorus and the presence of saturated rings are expected to reduc...
A more productive, but different, ocean after mitigation†

Reversibility studies suggest a lagged recovery of global mean sea surface temperatures after mitigation, raising the question of whether a similar lag is likely for marine net primary production (NPP). Here we assess NPP reversibility with a mitigation scenario in which projected Representative Concentration Pathway (RCP8.5) forcings are applied out to 2100, and then reversed over the course of the following century in a fully coupled carbon-climate earth system model. In contrast to the temperature lag, we find a rapid increase in global mean NPP, including an overshoot to values above contemporary means. The enhanced NPP arises from a transient imbalance between the cooling surface ocean and continued warming in subsurface waters, which weakens upper ocean density gradients, resulting in deeper mixing and enhanced surface nitrate. We also find a marine ecosystem regime shift as persistent silicate depletion results in increased prevalence of large, non-diatom phytoplankton.
Pathways to a lung cancer diagnosis

AbstractPurpose:The purpose of this qualitative descriptive study was to identify and describe pathways to a lung cancer diagnosis based on narratives of persons diagnosed with the disease.Data sources:Eleven adults with lung cancer were recruited from an academic thoracic oncology clinic in a large
Application of a simple analytical model to estimate effectiveness of radiation shielding for neutrons

Neutron dose equivalent rates have been measured for 800-MeV proton beam spills at the Los Alamos Meson Physics Facility. Neutron detectors were used to measure the neutron dose levels at a number of locations for each beam-spill test, and neutron energy spectra were measured for several beam-spill tests. Estimates of expected levels for various detector locations were made using a simple analytical model developed for 800-MeV proton beam spills. A comparison of measurements and model estimates indicates that the model is reasonably accurate in estimating the neutron dose equivalent rate for simple shielding geometries. The model fails for more complicated shielding geometries, where indirect contributions to the dose equivalent rate can dominate. >
The Public Health Enterprise: Examining Our Twenty-First-Century Policy Challenges

This paper examines the public health enterprise and its policy challenges in the twenty-first century. Among the many challenges public health faces, we include here collaboration across a broad range of stakeholders, the public health infrastructure, agreement on public health's essential services, preparedness, accountability and measurement, workforce, and a research agenda. Two Institute of Medicine reports on the future of public health have set the context for a more in-depth review of the public health workforce and infrastructure. Policy advocates must ask, however, why, if the way and the means are so clear, the public health system is still in disarray.
CALCULATION OF EIGENVECTOR DERIVATIVES FOR STRUCTURES WITH REPEATED EIGENVALUES

In structural optimization and system identification, eigenvector derivatives provide important information for updating design/model parameters. When the current parameter values yield repeated eigenvalues, it has not been possible previously to calculate unique eigenvector derivatives. Recent work has provided a method for determining unique eigenvalue derivatives for this case, but methods for calculating the eigenvector sensitivities have been incomplete. In this work, a complete method for calculation of repeated-root eigenvector derivatives is shown for the real, symmetric structural eigenproblem. The derivation is completed by using information from the second derivative of the eigen problem and is limited to the case of distinct eigenvalue sensitivities. As an example, the repeated-root eigenvector sensitivities are calculated for a simple three degree-of-freedom beam grillage. Comparisons of linear approximations (using these derivatives) to the calculated eigenvectors support the accuracy of the formulation.
Information-theoretic approach to interactive learning

The principles of statistical mechanics and information theory play an important role in learning and have inspired both theory and the design of numerous machine learning algorithms. The new aspect in this paper is a focus on integrating feedback from the learner. A quantitative approach to interactive learning and adaptive behavior is proposed, integrating model- and decision-making into one theoretical framework. This paper follows simple principles by requiring that the observer's world model and action policy should result in maximal predictive power at minimal complexity. Classes of optimal action policies and of optimal models are derived from an objective function that reflects this trade-off between prediction and complexity. The resulting optimal models then summarize, at different levels of abstraction, the process's causal organization in the presence of the learner's actions. A fundamental consequence of the proposed principle is that the learner's optimal action policies balance exploration and control as an emerging property. Interestingly, the explorative component is present in the absence of policy randomness, i.e. in the optimal deterministic behavior. This is a direct result of requiring maximal predictive power in the presence of feedback.
A novel VLSI technology to manufacture high-density thermoelectric cooling devices

This paper describes a novel integrated circuit technology to manufacture high-density thermoelectric devices on a semiconductor wafer. With no moving parts, a thermoelectric cooler operates quietly, allows cooling below ambient temperature, and may be used for temperature control or heating if the direction of current flow is reversed. By using a monolithic process to increase the number of thermoelectric couples, the proposed solid-state cooling technology can be combined with traditional air cooling, liquid cooling, and phase-change cooling to yield greater heat flux and provide better cooling capability.
A New Probability Inequality Using Typical Moments and Concentration Results

We present two probability inequalities. The simpler first inequality weakens both hypotheses in Hoffding-Azumaine quality. Using it, we generalize concentration results previously known for the uniform density for the TSP, MWST and Random Projections to long-tailed inhomogeneous distributions. The second more complicated inequality further weakens the moment requirements and using it, we prove the best possible concentration for the long-studied bin packing problem as well as some others.
Design of the C-Mod Advanced Outer Divertor

Operational requirements and research considerations make a high-temperature, toroidally continuous outer divertor an important aspect for future operation of the Alcator C-Mod tokamak. Leading edge melting of tiles, nonuniform heat loads, large electromagnetic forces, and localized impurity sources limit the performance of bulk plasmas. These issues can be addressed by the installation of a well-aligned, toroidally continuous outer divertor. In addition, future proposed long pulse operation of C-Mod will cause the temperature of the outer divertor to reach bulk temperatures as high as 500 °C–600 °C. This future operational requirement, combined with the strong temperature dependence of plasma surface interactions (especially fuel retention), makes a controllable, high-temperature outer divertor desirable and necessary. The design and development of the C-Mod advanced outer divertor is discussed.
Dispersed-phase structure of pressure-atomized sprays at various gas densities

The dispersed-phase structure of the dense-spray region of pressure-atom ized sprays was studied for atomization breakup conditions, considering large-scale (9.5 mm initial diameter) water jets in still-air at ambient pressures of 1, 2, and 4 atm, with both fully developed turbulent pipe flow and nonturbulent slug flow at the jet exit. Drop sizes and velocities and liquid-volume fractions and fluxes were measured using holography. Measurements were compared with predictions based on the locally homogeneous flow (LHF) approximation as well as recent correlations of drop sizes after primary breakup of turbulent and nonturbulent liquids. The dispersed-flow region beyond the liquid surface was relatively dilute (liquid-volume fractions less than 0.1%), with significant separated-flow effects throughout, and evidence of near-limit secondary breakup and drop deformation near the liquid surface. Turbulent primary breakup predictions were satisfactory at atmospheric pressure, where the correlation was developed, but failed to predict observed trends of decreasing drop sizes with increasing gas density due to aerodynamic effects; in contrast, the laminar primary breakup predictions successfully treated the relatively small effects of gas density for this breakup mechanism. Effects of liquid turbulence at the jet exit were qualitatively similar to single-phase flows, yielding faster mixing rates with increased turbulence levels even though drop sizes tended to increase as well. LHF predictions within the dispersed-flow region were only qualitatively correct due to significant separated-flow effects, but tended to improve as the ambient pressure and the distance from the jet exit increased.
Price Discovery for Stocker Cattle Futures and Options

Paper presented at the NCR-134 Conference on Applied Commodity Price Analysis,Forecasting, and Market Risk ManagementChicago, Illinois, April 17-18, 2000Copyright 2000 by Matthew A. Diersen and Nicole L. Klein. All rights reserved.Readers may make verbatim copies of this document for non-commercial purposes by anymeans, provided that this copyright notice appears on all such copies.
Labor Supply Responses to Marginal Social Security Benefits: Evidence from Discontinuities

Abstract A key question for Social Security reform is whether workers respond to the link on the margin between the Social Security taxes they pay and the Social Security benefits they will receive. We estimate the effects of the marginal Social Security benefits that accrue with additional earnings on three measures of labor supply: retirement age, hours, and labor earnings. We develop a new approach to identifying these incentive effects by exploiting five provisions in the Social Security benefit rules that generate discontinuities in marginal benefits or non-linearities in marginal benefits that converge to discontinuities as uncertainty about the future is resolved. We find that individuals approaching retirement (age 52 and older) respond to the Social Security tax-benefit link on the extensive margin of their labor supply decisions: we estimate that a 10% increase in the net-of-tax share reduces the two-year retirement hazard by a statistically significant 2.0 percentage points from a base rate of 15%. The evidence with regard to labor supply responses on the intensive margin is more mixed: we estimate that the elasticity of hours with respect to the net-of-tax share is 0.42 and statistically significant, but we do not find a statistically significant earnings elasticity. Though we lack statistical power to estimate results within subsamples precisely, the retirement response is driven mostly by the female subsample, while the hours response comes from the male subsample.
The Rise of the Vulcans

In this introductory review presented at the IAU Symposium 253 "Transiting Plan- ets", I summarize the path from the initial 1995 radial-velocity discovery of hot Jupiters to the current rich panoply of investigations that are afforded when such objects are observed to transit their parent stars. Forty transiting exoplanets are now known, and the time for that population to double has dropped below one year. It is only for these objects that we have direct estimates of their masses and radii, and for which (at the current time) we can undertake direct studies of the chemistries and dynamics of their atmospheres. Informed by the successes of hot Jupiter studies, I outline a path for the spectroscopic study of certain habitable exoplanets that obviates the need for direct imaging.
Stochastic State Transitions Give Rise to Phenotypic Equilibrium in Populations of Cancer Cells

Cancer cells within individual tumors often exist in distinct phenotypic states that differ in functional attributes. While cancer cell populations typically display distinctive equilibria in the proportion of cells in various states, the mechanisms by which this occurs are poorly understood. Here, we study the dynamics of phenotypic proportions in human breast cancer cell lines. We show that subpopulations of cells purified for a given phenotypic state return towards equilibrium proportions over time. These observations can be explained by a Markov model in which cells transition stochastically between states. A prediction of this model is that, given certain conditions, any subpopulation of cells will return to equilibrium phenotypic proportions over time. A second prediction is that breast cancer stem-like cells arise de novo from non-stem-like cells. These findings contribute to our understanding of cancer heterogeneity and reveal how stochasticity in single-cell behaviors promotes phenotypic equilibrium in populations of cancer cells.
FLUX DENSITIES AND RADIO POLARIZATION CHARACTERISTICS OF TWO VELA-LIKE PULSARS

We report on dual-frequency radio polarimetry observations of two young, energetic pulsars, PSRs J0940� 5428 andJ1301� 6305.ThesewereamongthefirstVela-likepulsarsdiscoveredintheParkesmultibeamsurvey.Weconducted observations of these pulsars with the Australia Telescope Compact Array (ATCA) at center frequencies of 1384 and 2496 MHz using pulsar gating while preserving full Stokes parameters. After correcting for bandwidth depolarization, we measured polarization characteristics, flux densities, and rotation measures for these pulsars. The spectral indices derived from the ATCA data are shallow but still consistent with values seen for pulsars of this type. The rotationmeasures for bothpulsars are consistent withthose reportedrecentlyusingdata from the Parkes telescope, and both pulsars have highly linearly polarized pulse profiles at both 1384 and 2496 MHz. Our results support a previously noted correlation between a high degree of linear polarization, shallow spectral index, and large spin-down luminosity.
Resolution of Some Open Problems Concerning Multiple Zeta Evaluations of Arbitrary Depth

We prove some new evaluations for multiple polylogarithms of arbitrary depth. The simplest of our results is a multiple zeta evaluation one order of complexity beyond the well-known Broadhurst–Zagier formula. Other results we provide settle three of the remaining outstanding conjectures of Borwein, Bradley, and Broadhurst. A complete treatment of a certain arbitrary depth class of periodic alternating unit Euler sums is also given.
Health and Labour Market Participation in Uganda

The paucity of non-agricultural paid employment, and under utilization of female labour in Uganda, and other sub-Saharan African countries, is often seen to be the next major obstacle to further poverty reduction and development in the region. Despite thi
On the discriminant locus of a Lagrangian fibration

Let \(X \rightarrow {\mathbb{P}}^n\) be an irreducible holomorphic symplectic manifold of dimension 2n fibred over \({\mathbb{P}}^n\) . Matsushita proved that the generic fibre is a holomorphic Lagrangian abelian variety. In this article we study the discriminant locus \(\Delta\subset{\mathbb{P}}^n\) parametrizing singular fibres. Our main result is a formula for the degree of Δ, leading to bounds on the degree when X is a fourfold.
A synthesis of (+)-saxitoxin.

An asymmetric synthesis of the bis-guanidinium poison, (+)-saxitoxin (STX), is described. Commencing from an N,O-acetal starting material made readily available through sulfamate ester C−H amination, the completed route to STX showcases the utility of oxathiazinane dioxide heterocycles for the assembly of polyfunctionalized amine derivatives. In the final preparative stages, an unusual nine-membered ring guanidine intermediate is oxidized selectively and made to undergo dehydrative cyclization to afford the tricyclic core of the natural product. Access to STX and related structures will provide unique pharmacological tools for the study of voltage-regulated Na+ ion channel proteins.
Spaceborne lidar calibration from cirrus and molecular backscatter returns

In order to make optimal quantitative use of multiwavelength spaceborne lidar data, it is essential that the lidar be well calibrated. Due to system gain/efficiency changes that can be expected to occur during the course of a shuttle or satellite mission, it is essential to employ a calibration approach that can be implemented on-orbit, preferably repeatable at least a few times per orbit. For wavelengths less than about 550 nm, in situ calibration can be accomplished via normalization to high-altitude nearly molecular scattering regions. However, for longer wavelengths beyond about 800 nm, particularly the popular Nd: YAG fundamental wavelength at 1064 nm, the Rayleigh normalization approach becomes questionable due to both an inherently weaker signal and a stronger, variable, and somewhat unknown aerosol scattering contribution. For lidars operating at both longer and shorter wavelengths, a viable approach is to retrieve the longer wavelength calibrations ratioed to the shorter wavelength calibrations via comparisons of spectral backscatter from known/quantifiable scatterers. Cirrus clouds are good for this purpose because they occur at high altitudes with significant frequency and provide strong nearly spectrally flat backscatter. This paper presents both the molecular normalization and cirrus spectral backscatter ratio calibration approaches, including results obtained from case studies of lidar data collected during the LITE shuttle mission. Attention is focused on developing a simple autonomous approach applicable to satellite lidar missions such as Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) and the Geoscience Laser Altimeter System (GLAS).
Web-based student evaluations of professors: The relations between perceived Quality, Easiness and Sexiness

College students critique their professors' teaching at RateMyProfessors.com, a web page where students anonymously rate their professors on Quality, Easiness, and Sexiness. Using the self-selected data from this public forum, we examine the relations between quality, easiness, and sexiness for 3190 professors at 25 universities. For faculty with at least ten student posts, the correlation between quality and easiness is 0.61, and the correlation between quality and sexiness is 0.30. Using simple linear regression, we find that about half of the variation in quality is a function of easiness and sexiness. When grouped into sexy and non-sexy professors, the data reveal that students give sexy-rated professors higher quality and easiness scores. If these findings reflect the thinking of American college students when they complete in-class student opinion surveys, then universities need to rethink the validity of student opinion surveys as a measure of teaching effectiveness. High student opinion survey sco...
Development of QSAR models to predict and interpret the biological activity of artemisinin analogues.

This work presents the development of Quantitative Structure−Activity Relationship (QSAR) models to predict the biological activity of 179 artemisinin analogues. The structures of the molecules are...
Uncertainties in adaptive maximum entropy frequency estimators

For a real sinusoid in white noise, the weight vector noise associated with an adaptive maximum entropy (AME) frequency estimator causes the spectrum peak to shift away from the input frequency. For a long adaptive filter, approximate expressions for this estimator's peak value and frequency variance are derived. For low SNR, the probability of obtaining a spurious peak is evaluated.
Redox, haem and CO in enzymatic catalysis and regulation

The present paper describes general principles of redox catalysis and redox regulation in two diverse systems. The first is microbial metabolism of CO by the Wood–Ljungdahl pathway, which involves the conversion of CO or H 2 /CO 2 into acetyl-CoA, which then serves as a source of ATP and cell carbon. The focus is on two enzymes that make and utilize CO, CODH (carbon monoxide dehydrogenase) and ACS (acetyl-CoA synthase). In this pathway, CODH converts CO 2 into CO and ACS generates acetyl-CoA in a reaction involving Ni·CO, methyl-Ni and acetyl-Ni as catalytic intermediates. A 70 A (1 A=0.1 nm) channel guides CO, generated at the active site of CODH, to a CO ‘cage’ near the ACS active site to sequester this reactive species and assure its rapid availability to participate in a kinetically coupled reaction with an unstable Ni(I) state that was recently trapped by photolytic, rapid kinetic and spectroscopic studies. The present paper also describes studies of two haem-regulated systems that involve a principle of metabolic regulation interlinking redox, haem and CO. Recent studies with HO2 (haem oxygenase-2), a K + ion channel (the BK channel) and a nuclear receptor (Rev-Erb) demonstrate that this mode of regulation involves a thiol–disulfide redox switch that regulates haem binding and that gas signalling molecules (CO and NO) modulate the effect of haem.
One-step synthesis of heterocyclic privileged medicinal scaffolds by a multicomponent reaction of malononitrile with aldehydes and thiols.

Heterocyclic privileged medicinal scaffolds involving pyridine, 1,4-dihydropyridine, chromeno[2,3-b]pyridine, and dihydro-1,4-dithiepine frameworks are prepared via a single-step multicomponent reaction of structurally diverse aldehydes with various thiols and malononitrile. Mechanistic studies of the synthetic pathway leading to pyridines reveal that 1,4-dihydropyridines undergo oxidation by the intermediate Knoevenagel adducts rather than by air oxygen. The use of o,o‘-disubstituted aromatic aldehydes leads to the corresponding 1,4-dihydropyridines, whereas salicylic aldehydes result in chromeno[2,3-b]pyridines. Reactions of ethanedithiol as a thiol component produce dimeric pyridines with sterically unencumbered aldehydes, while o,o‘-disubstituted aromatic aldehydes give dihydro-1,4-dithiepines. Thus, depending on the aldehyde and thiol types, diverse libraries of medicinally relevant compounds can be prepared by a simple one-step process involving no chromatography.
What Do We Know So Far about Multigenerational Mobility

“Multigenerational mobility” refers to the associations in socioeconomic status across three or more generations. This article begins by summarizing the longstanding but recently growing empirical literature on multigenerational mobility. It then discusses multiple theoretical interpretations of the empirical patterns, including the one recently proposed in Gregory Clark’s book The Son Also Rises.
Biorthogonal Eigenfunction System in the Triple-Deck Limit

The solutions of receptivity problems for a periodic-in-time actuator placed on the wall in a two-dimensional boundary layer and for a two-dimensional hump are discussed within the scope of the biorthogonal eigenfunction expansion technique in the limit of high Reynolds number when the triple-deck scaling is imposed. It is shown that the solutions obtained with the help of the biorthogonal eigenfunction system are equivalent to the solutions derived within the scope of the triple-deck theory.
A Systematic Approach to Modeling Impedances and Current Distribution in Planar Magnetics

Planar magnetic components using printed circuit board (pcb) windings are attractive due to their high repeatability, good thermal performance, and usefulness for realizing intricate winding patterns. To enable higher system integration at high switching frequency, more sophisticated methods that can rapidly and accurately model planar magnetics are needed. This paper develops a systematic approach to modeling impedances and current distribution in planar magnetics based on a lumped circuit model named as the modular layer model (MLM). Stacked pcb layers are modeled as repeating modular impedance networks, with additional modular impedances representing the magnetic core, air gaps, and vias. The model captures skin and proximity effects, and enables accurate predictions of impedances, losses, stored reactive energy, and current sharing among windings. The MLM can be used to simulate circuits incorporating planar magnetics, to visualize the electromagnetic fields, and to extract parameters for magnetic models by simulations, among many other applications. The modeling results are checked with results of previous theories and finite-element-modeling approaches, with good matching presented. A group of planar magnetic devices, including transformers and inductors with various winding patterns, are prototyped, and measured to validate the proposed approach and clarify the boundaries of its applicability.
Teaching Opportunity Cost in an Emissions Permit Experiment

This paper describes an individual choice experiment that can be used to teach students how to correctly account for opportunity costs in production decisions. Students play the role of producers t ...
High-speed architectures for parallel long BCH encoders

Long Bose-Chaudhuri-Hocquenghen (BCH) codes are used as the outer error correcting codes in the second-generation Digital Video Broadcasting Standard from the European Telecommunications Standard Institute. These codes can achieve around 0.6-dB additional coding gain over Reed-Solomon codes with similar code rate and codeword length in long-haul optical communication systems. BCH encoders are conventionally implemented by a linear feedback shift register architecture. High-speed applications of BCH codes require parallel implementation of the encoders. In addition, long BCH encoders suffer from the effect of large fanout. In this paper, three novel architectures are proposed to reduce the achievable minimum clock period for long BCH encoders after the fanout bottleneck has been eliminated. For an (8191, 7684) BCH code, compared to the original 32-parallel BCH encoder architecture without fanout bottleneck, the proposed architectures can achieve a speedup of over 100%.
Superreplication under model uncertainty in discrete time

We study the superreplication of contingent claims under model uncertainty in discrete time. We show that optimal superreplicating strategies exist in a general measure-theoretic setting; moreover, we characterize the minimal superreplication price as the supremum over all continuous linear pricing functionals on a suitable Banach space. The main ingredient is a closedness result for the set of claims which can be superreplicated from zero capital; its proof relies on medial limits.
Spectral purity for far infrared grating spectroscopy.

A far ir grating spectrometer of the Ebert type has been constructed to cover the range from 10 cm−1 to 160 cm−1. A technique for quantitatively measuring the spectral purity of this instrument is presented. Filter curves for the reflection filter gratings used with the spectrometer are given for radiations polarized parallel and perpendicular to the groove length. It is found that, with a 20° blaze angle and the plane of incidence of the radiation parallel to the groove length, polarization effects due to the filters are small. In fact, the filters are very efficient and possess sharp cutoff characteristics in both polarizations when used in this fashion. The measured spectral purity of the spectrometer is better than 95% throughout most of its operating range. This result is consistent with purity estimates from absorption experiments on water vapor lines in the region from 195 μ, to 300 μ. Experimental results pertaining to far ir solid-state physics research are also briefly discussed.
Design of trustworthy fielded sensor networks

Sensor networks hold great promise as tools in the study of complex natural systems, in a broad range of areas from terrestrial ecology through to seismology. The primary goal in a scientific experiment is computation of some inference from the observations and available models. From this basic problem flows a broad set of practical and theoretical issues, among them assurance of data integrity, sufficiency of data to support the inferences made concerning models/hypotheses, and what tools and hardware are required not just to take observations but enable a community of non-engineers to participate in and adapt a sequence of experiments as new observations are obtained. The resulting constraints for designing systems for such purposes are quite different from those commonly assumed in the infancy of sensor network research, and even now in much ongoing systems research. We describe these constraints in light of experience in deploying sensor networks in support of scientific study at the center for embedded networked sensors (CENS).
What the Ancient Greeks Can Tell Us About Democracy

The question of what the ancient Greeks can tell us about democracy can be answered by reference to three fields that have traditionally been pursued with little reference to one another: ancient history, classical political theory, and political science. These fields have been coming into more fruitful contact over the past 20 years, as evidenced by a spate of interdisciplinary work. Historians, political theorists, and political scientists interested in classical Greek democracy are increasingly capable of leveraging results across disciplinary lines. As a result, the classical Greek experience has more to tell us about the origins and definition of democracy, and about the relationships between participatory democracy and formal institutions, rhetoric, civic identity, political values, political criticism, war, economy, culture, and religion.
Complementary filter design for testing of IS-95 code division multiple access wireless communication systems

In this paper, a simple design of a complementary filter is presented for performance measurement of an IS-95 code division multiple access wireless communication system (1995). The complementary filter is required to meet the design requirements, which are specified in IS-97 document (1994). The purpose of employing the complementary filter in test equipment is to remove intersymbol interference introduced by the base station transmit-filter and the transmit-phase equalizer. Five window functions, which do not affect the desirable response at the proper sampling times, are applied to the desirable output. The output of a window Is set to be the output of the complementary filter. Then, the complementary filter is obtained by taking a deconvolution of the output response of the window with the impulse response resulted by cascading the base station transmit-filter and the transmit-equalizer. It is found that the output of the complementary filter with the Kaiser window function meets all requirements specified in IS-97. In addition, it is observed that the Kaiser window has the smallest number of the filter coefficients among all windows considered in this paper. Therefore, the complementary filter with the Kaiser window is recommended for implementation of the IS-95 system measurement.
Bounding the Transient Response of Structures to Uncertain Disturbances

An analytical method is presented for bounding the peak transient response of a structure to an arbitrary, dynamic input force vector of given total magnitude. Since the method is based on the linear operator norm for the multivariable impulse response of the structural system, it does not require either a simulation or a numerical search to bound the worst-case response. Instead, the bound is computed directly from the structural eigenmodes. The method reported in this paper is a generalization of existing bounding methods for single-input/single-output methods to the more practical case of vector-valued forces and vector-valued responses. In addition, the paper presents a method for computing one of the possible input force vector tune histories that will excite a structural response equal to the bounded value. This worst-case input force is proposed as a candidate for force time histories to be used in structural qualification testing.
Ionization Energies and Electron Mobilities in Phosphorus- and Nitrogen-Implanted 4H-Silicon Carbide

Comparisons are made between the carrier concentrations, ionization energies, and electron mobilities in 4H–SiC samples implanted with similar doses of nitrogen or phosphorus and annealed at 1300 or 1700 °C for 10 min in argon. The objective of the research is to determine which element may yield lower resistance 4H–SiC. Ionization energies of 53 and 93 meV are measured from phosphorus-implanted 4H–SiC, and are assigned to the hexagonal and cubic lattice positions in 4H–SiC, respectively. The corresponding ionization energies for nitrogen-implanted 4H–SiC are 42 and 84 meV, respectively. Phosphorus is not activated to the same extent that nitrogen is, and the carrier concentrations are about a factor of five lower for phosphorus-implanted 4H–SiC annealed at 1300 °C than for nitrogen-implanted 4H–SiC annealed at the same temperature. A higher mobility for phosphorus-implanted 4H–SiC is observed, but is not sufficiently high to offset the lower carrier concentration of this material. For the doses considered in this study, the resistivity of nitrogen-implanted 4H–SiC is lower than the resistivity of phosphorus-implanted 4H–SiC following anneals at either 1300 or 1700 °C.
Model-Based Three-Dimensional Interpretations of Two-Dimensional Images

ACRONYM is a comprehensive domain independent model-based system for vision and manipulation related tasks. Many of its submodules and representations have been described elsewhere. Here the derivation and use of invariants for image feature prediction is described. Predictions of image features and their relations are made from three-dimensional geometric models. Instructions are generated which teli the interpretation algorithms how to make use of image feature measurements to derive three-dimensional size, structural, and spatial constraints on the original three-dimensional models. Some preliminary examples of ACRONYM's interpretations of aerial images are shown.
The changing demographic and economic structure of nonmetropolitan areas in the United States

The forces underlying contemporary nonmetropolitan popula tion trends differ substantially from those that operated during the 1960s. Multivariate analyses of county-level population change between 1960-1970 and 1970-1974 support two major conclusions: (1) Migration into entirely rural nonmetropolitan counties has accelerated, evidently signaling the emergence in the 1970s of a new (or at least more complex) spatial pattern of settlement; and (2) previous growth advantages associated with manufacturing and gov ernment related activity appear to have diminished, and retirement and recre ation have emerged as important growth-inducing activities.The first finding has important implications for the rationale underlying U.S. regional development policy, in which urban nodes designated as "growth centers" figure as a necessary element for a region's takeoff or reversal of its economic decline. Under present circumstances, that rationale may define the prospects for nonmetropolitan development too narrowly by p...
Expected degree for RNA secondary structure networks

Consider the network of all secondary structures of a given RNA sequence, where nodes are connected when the corresponding structures have base pair distance one. The expected degree of the network is the average number of neighbors, where average may be computed with respect to the either the uniform or Boltzmann probability. Here, we describe the first algorithm, RNAexpNumNbors, that can compute the expected number of neighbors, or expected network degree, of an input sequence. For RNA sequences from the Rfam database, the expected degree is significantly less than the constrained minimum free energy structure, defined to have minimum free energy (MFE) over all structures consistent with the Rfam consensus structure. The expected degree of structural RNAs, such as purine riboswitches, paradoxically appears to be smaller than that of random RNA, yet the difference between the degree of the MFE structure and the expected degree is larger than that of random RNA. Expected degree does not seem to correlate with standard structural diversity measures of RNA, such as positional entropy and ensemble defect. The program RNAexpNumNbors is written in C, runs in cubic time and quadratic space, and is publicly available at http://bioinformatics.bc.edu/clotelab/RNAexpNumNbors.
Asymmetric Synthesis of Cyclic α-Amino Phosphonates Using Masked Oxo Sulfinimines (N-Sulfinyl Imines)

Five-, six-, and seven-membered cyclic α-amino phosphonates, amino acid surrogates, are prepared in enantiomerically pure form via the highly diastereomeric addition of metal phosphonates to masked oxo sulfinimines. Hydrolysis of the resulting masked oxo α-amino phosphonates followed by reduction of the intermediate cyclic imino phosphonates affords the title compounds in good yield.
Interference Drag of a Turbulent Junction Vortex

The interference drag identified with the junction of a streamlined cylindrical body and a flat plate was investigated. The junction drag was calculated, from a set of detailed, self consistent, high quality data using a control volume approach.
Unrestricted products of contractions in Banach spaces

Let $X$ be a reflexive Banach space such that for any $x \ne 0$ the set $$ \{x^* \in X^*: \text {$\|x^*\|=1$ and $x^*(x)=\|x\|$}\} $$ is compact. We prove that any unrestricted product of of a finite number of $(W)$ contractions on $X$ converges weakly.
Molecular-dynamics simulations of fracture: An overview of system size and other effects

The authors have studied brittle and ductile behavior and their dependence on system size and interaction potentials, using molecular-dynamics (MD) simulations. By carefully embedding a single sharp crack in two- and three-dimensional crystals, and using a variant of the efficient sound-absorbing reservoir of Holian and Ravelo [Phys. Rev. B 51, 11275 (1995)], they have been able to probe both the static and dynamic crack regimes. Their treatment of boundary and initial conditions allows them to elucidate early crack propagation mechanisms under delicate overloading, all the way up to the more extreme dynamic crack-propagation regime, for much longer times than has been possible heretofore (before unwanted boundary effects predominate). For example, the authors have used graphical display of atomic velocities, forces, and potential energies to expose the presence of localized phonon-like modes near the moving crack tip, just prior to dislocation emission and crack-branching events. They find that their careful MD method is able to reproduce the ZCT brittle-ductile criterion for short-range pair potentials [static lattice Green`s function calculations of Zhou, Carlsson, and Thomson, Phys. Rev. Letters 72, 852 (1994)]. They report on progress they have made in large-scale 3D simulations in samples that are thick enough to display realistic behaviormore » at the crack tip, including emission of dislocation loops. Such calculations, using their careful treatment of boundary and initial conditions -- especially important in 3D -- have the promise of opening up new vistas in fracture research.« less
Trace-Based memory aliasing across program versions

One of the major costs of software development is associated with testing and validation of successive versions of software systems. An important problem encountered in testing and validation is memory aliasing, which involves correlation of variables across program versions. This is useful to ensure that existing invariants are preserved in newer versions and to match program execution histories. Recent work in this area has focused on trace-based techniques to better isolate affected regions. A variation of this general approach considers memory operations to generate more refined impact sets. The utility of such an approach eventually relies on the ability to effectively recognize aliases. In this paper, we address the general memory aliasing problem and present a probabilistic trace-based technique for correlating memory locations across execution traces, and associated variables in program versions. Our approach is based on computing the log-odds ratio, which defines the affinity of locations based on observed patterns. As part of the aliasing process, the traces for initial test inputs are aligned without considering aliasing. From the aligned traces, the log-odds ratio of the memory locations is computed. Subsequently, aliasing is used for alignment of successive traces. Our technique can easily be extended to other applications where detecting aliasing is necessary. As a case study, we implement and use our approach in dynamic impact analysis for detecting variations across program versions. Using detailed experiments on real versions of software systems, we observe significant improvements in detection of affected regions when aliasing occurs.
Progress and continuing challenges in GaSb-based III-V alloys and heterostructures grown by organometallic vapor-phase epitaxy

Abstract This paper discusses progress in the preparation of mid-IR GaSb-based III–V materials grown by organometallic vapor-phase epitaxy (OMVPE). The growth of these materials is complex, and fundamental and practical issues associated with their growth are outlined. Approaches that have been explored to further improve properties and performance are briefly reviewed. Recent materials and device results on GaInAsSb bulk layers and GaInAsSb/AlGaAsSb heterostructures, grown lattice matched to GaSb, are presented. State-of-the-art GaInAsSb materials and thermophotovoltaic devices have been achieved. This progress establishes the high potential of OMVPE for mid-IR GaSb-based devices.
Effects of clumping on temperature – I. Externally heated clouds

We present a study of radiative transfer in dusty, clumpy star-forming regions. A series of self-consistent, 3D, continuum radiative transfer models are constructed for a grid of models parametrized by central luminosity, filling factor, clump radius and face-averaged optical depth. The temperature distribution within the clouds is studied as a function of this parametrization. Among our results, we find that: (i) the effective optical depth in clumpy regions is less than in equivalent homogeneous regions of the same average optical depth, leading to a deeper penetration of heating radiation in clumpy clouds, and temperatures higher by over 60 per cent; (ii) penetration of radiation is driven by the fraction of open sky (FOS) - which is a measure of the fraction of solid angle along which no clumps exist; (iii) FOS increases as clump radius increases and as filling factor decreases; (iv) for values of FOS >0.6-0.8 the sky is sufficiently 'open' that the temperature distribution is relatively insensitive to FOS; (v) the physical process by which radiation penetrates is preferentially through streaming of radiation between clumps as opposed to diffusion through clumps; (vi) filling factor always dominates the determination of the temperature distribution for large optical depths, and for small clump radii at smaller optical depths; (vii) at lower face-averaged optical depths, the temperature distribution is most sensitive to filling factors of 1-10 per cent, in accordance with many observations; (viii) direct shadowing by clumps can be important for distances approximately one clump radius behind a clump.