cssi/SciSciGPT-SciSciNet huggingface dataset:
Novel Concepts for Constraint Treatments and Approximations in Efficient Structural Synthesis

The paper presents some new concepts for efficient treatment of large number of constraints. The ideas are based on finding effective ways of reducing the number of active constraints without degrading thei r overall behavioral characteristics or a ltering the essential nature of the original design problem. This has led to a set o f t hree distinct and new concepts which are discussed here. The paper first presents a generalized concept of "dial -inu form of constraint approximation, which can supply a hierarchy of conforming constraint approximati on -- forms for increasing conservativeness and/or accuracy. It contains two tuning parameters, which can be used to control the quality o f the constraint approximations for most structural types (truss, frame, panel, reinforced, etc. ) and finite elements (membrane, bending, shear, plate, shell, etc.) of interest. Second, the paper presents a concept of partitioning the mixed constraint set according to their types into distinct subsets. This allows control of the constraint behaviors in a logical manner. Third, the paper introduces a concept of e ffectively collapsing the constraints which occur in packets of high concentrations. A d eterminate truss, an indeterminate truss and a thin beam are used as examples.
A flash photolysis resonance fluorescence investigation of the reactions of Oxygen O(3P) atoms with aliphatic ethers and diethers in the gas phase

Rate constants for the gas phase reactions of O( 3 P) atoms with a series of symmetric aliphatic ethers have been determined using the flash photolysis resonance fluorescence technique over the temperature range 240-400 K. The Arrhenius parameters derived from these data are (in units of cm 3 molecule −1 s −1 ): dimethyl ether, k=(5.39±1.94)×10 −12 exp([(−1320±120)/T]; diethyl ether, k=(1.42±0.18)×10 −11 exp([(−1070±40)/T]; di-n-propyl ether, k=(1.41±0.21)×10 −11 exp([(−960±50)/T]; di-n-butyl ether, k=(1.37±0.29)×10 −11 exp([(−880±70)/T]; di-n-pentyl ether, k=(1.26±0.84)×10 −11 exp([(−780±20/T]. The error limits are two standard deviations derived from the least-square fit. Rate constants for several other ethers were determined only at 298 K. The values obtained were (in units of 10 −14 cm 3 molecule −1 s −1 ): tetrahydrofuran (37.5±1.1); 1,4-dioxane (6.81±0.46); diethoxymethane (40.4±1.8); ethyl-t-butylether (37.0±1.3); and methyl-t-amylether (57.3±2.3)
Finite Element Algorithm for Frictionless Contact of Porous Permeable Media Under Finite Deformation and Sliding

This study formulates and implements a finite element contact algorithm for solid-fluid (biphasic) mixtures, accommodating both finite deformation and sliding. The finite element source code is made available to the general public. The algorithm uses a penalty method regularized with an augmented Lagrangian method to enforce the continuity of contact traction and normal component of fluid flux across the contact interface. The formulation addresses the need to automatically enforce free-draining conditions outside of the contact interface. The accuracy of the implementation is verified using contact problems, for which exact solutions are obtained by alternative analyses. Illustrations are also provided that demonstrate large deformations and sliding under configurations relevant to biomechanical applications such as articular contact. This study addresses an important computational need in the biomechanics of porous-permeable soft tissues. Placing the source code in the public domain provides a useful resource to the biomechanics community.
A dynamic data structure for flexible molecular maintenance and informatics

Motivation: We present the ‘Dynamic Packing Grid’ (DPG), a neighborhood data structure for maintaining and manipulating flexible molecules and assemblies, for efficient computation of binding affinities in drug design or in molecular dynamics calculations. Results:DPG can efficiently maintain the molecular surface using only linear space and supports quasi-constant time insertion, deletion and movement (i.e. updates) of atoms or groups of atoms. DPG also supports constant time neighborhood queries from arbitrary points. Our results for maintenance of molecular surface and polarization energy computations using DPG exhibit marked improvement in time and space requirements. Availability: http://www.cs.utexas.edu/~bajaj/cvc/software/DPG.shtml Contact: bajaj@cs.utexas.edu Supplementary information:Supplementary data are available at Bioinformatics online.
Chiral gauge theories from D-branes

Abstract We construct brane configurations leading to chiral four dimensional N =1 supersymmetric gauge theories. The brane realizations consist of intersecting Neveu-Schwarz five-branes and Dirichlet four-branes in non-flat spacetime backgrounds. We discuss in some detail the construction in a C 2 / Z M orbifold background. The infrared theory on the four-brane worldvolume is a four dimensional N =1 SU ( N ) M gauge theory with chiral matter representations. We discuss various consistency checks and show that the spectral curves describing the Coulomb phase of the theory can be obtained once the orbifold brane construction is embedded in M-theory. We also discuss the addition of extra vectorlike matter and other interesting generalizations.
Design and testing of a power electronic synthetic inductor

In many applications inductors are often replaced with circuits, typically based upon operational amplifiers, which emulate an inductance for reasons of package size or to closer approximate the desired ideal behaviour. A power electronic synthetic inductor offers an alternative circuit which can emulate an inductor with relatively low power consumption, as well as provide a flexible circuit topology that is not limited to inductive behaviour. In this article, a power electronic synthetic inductor topology and control system is developed. A prototype synthetic inductor was built and tested, and its operation was explored and compared with an operational-amplifier-based synthetic inductor. A minor modification of the circuit allows the emulation of a negative resistance in parallel with the synthesised inductor, which can increase the quality factor of the system beyond that associated with an ideal inductor. Experimental results reveal that the power electronic synthetic inductor has significantly lower p...
Computation of three-dimensional viscous flows using a space-marching method

A space-marching method, developed to compute three-dimensional flows for internal geometries, has been utilized to predict viscous flows through a curved duct and over a swept wing. The Navier-Stokes equations have been posed as an initial value problem by neglecting the streamwise viscous diffusion terms and by treating the pressure gradient as a known source term. The resulting equations have been solved by a non-iterative (single pass) algorithm at each streamwise step. The results are compared with earlier computations (based on iterative methods) and the experimental data. The agreement between the present predictions, the experimental data, and the earlier predictions is good for the cases computed. The computation time is only a fraction of the iterative methods.
Production-Inventory Systems with Lost Sales and Compound Poisson Demands

This paper considers a continuous-review, single-product, production-inventory system with a constant replenishment rate, compound Poisson demands, and lost sales. Two objective functions that represent metrics of operational costs are considered: 1 the sum of the expected discounted inventory holding costs and lost-sales penalties, both over an infinite time horizon, given an initial inventory level; and 2 the long-run time average of the same costs. The goal is to minimize these cost metrics with respect to the replenishment rate. It is, however, not possible to obtain closed-form expressions for the aforementioned cost functions directly in terms of positive replenishment rate PRR. To overcome this difficulty, we construct a bijection from the PRR space to the space of positive roots of Lundberg's fundamental equation, to be referred to as the Lundberg positive rootLPR space. This transformation allows us to derive closed-form expressions for the aforementioned cost metrics with respect to the LPR variable, in lieu of the PRR variable. We then proceed to solve the optimization problem in the LPR space and, finally, recover the optimal replenishment rate from the optimal LPR variable via the inverse bijection. For the special cases of constant or loss-proportional penalty and exponentially distributed demand sizes, we obtain simpler explicit formulas for the optimal replenishment rate.
A single user evaluation of the Gamma database machine

This paper presents the results of an initial performance evaluation of the Gamma database machine based on an expanded version of the single-user Wisconsin benchmark. In our experiments we measured the effect of relation size and indices on response time for selection, join, and aggregation queries, and single-tuple updates. A Teradata DBC/1012 database machine of similar size is used as a basis for interpreting the results obtained. We analyze and interpret the results of these experiments based on our understanding of the system hardware and software, and conclude with an assessment of the strengths and weaknesses of the two machines.
Behavioral Disinhibition and the Development of Early-Onset Addiction: Common and Specific Influences

Research on substance use disorders is often compartmentalized, focused on understanding addiction to one substance or substance class at a time. Although this approach has contributed significantly to knowledge about addictions, early-onset substance use disorders appear to share common etiology with each other and with other disorders, traits, behaviors, and endophenotypes associated with behavioral disinhibition. We propose that a common genetic liability to behavioral disinhibition underlies the co-occurrence of these externalizing attributes. This liability is expressed in part through brain mechanisms related to cognitive control, impulsivity, and sensitivity to reward, all of which are maturing during adolescence. During this important transitional period, problem behaviors emerge, including the initiation of substance use. Exposure to various environmental risks further amplifies the risk associated with the common liability, increasing the likelihood of addiction generally. Specific environmental and genetic factors ultimately contribute to the differentiation among externalizing disorders.
Comparative Efficacy Trials (Phase III Studies)

A comparative efficacy trial (a phase III study) is a clinical trial that is designed to compare the efficacy of an experimental treatment with that of a control treatment (active or a placebo). This article provides a brief introduction to the design and analysis of phase III trials. The issues discussed include randomization and blinding, selection of populations for study, selection of efficacy endpoints, the risk of type I and II errors, the determination of sample size, multicenter trials, interim analysis, and the assessment and comparison of treatment effects between/among different treatment groups. Keywords: comparative efficacy trials; control treatment; equivalence trials; experimental treatment; group sequential design; noninferiority clinical trials; phase III studies; power analysis; sample size; superiority trials
Rhodium (II) catalyzed cyclizations of α-diazo substituted alkynes. A new mode of reaction

Abstract Treatment of several o-alkyne-enyl substituted α-diazoacetophenone derivatives with Rh 2 OAc 4 results in cyclopropenyl substituted indenones which undergo a subsequent 2+2-dimerization reaction.
Cell motility on micropatterned treadmills and tracks

Surfaces micropatterned with disjointed cell adhesive/non-adhesive regions allow for precise control of cell shape, internal organization and function. In particular, substrates prepared by the reaction–diffusion ASoMic (Anisotropic Solid Microetching) method localize cells onto transparent micro-islands or tracks surrounded by an opaque, adhesion-resistant background. ASoMic is compatible with several important imaging modalities (e.g. wide-field, fluorescent, TIRF and confocal microscopies), and can be used to study and quantify various intracellular and cellular processes related to cell motility. For cells constrained on the islands, the imposed geometry controls spatial organization of the cytoskeleton, while the transparency of the islands allows for real-time analysis of cytoskeletal dynamics. For cells on transparent, linear tracks, the high optical contrast between these adhesive regions and the surrounding non-adhesive background allows for straightforward quantification of the key parameters describing cell motility. Both types of systems provide analytical-quality data that can assist fundamental studies of cell locomotion and can provide a technological basis for cell motility microassays.
Designing surveys for tests of gravity.

Modified gravity theories may provide an alternative to dark energy to explain cosmic acceleration. We argue that the observational programme developed to test dark energy needs to be augmented to capture new tests of gravity on astrophysical scales. Several distinct signatures of gravity theories exist outside the ‘linear’ regime, especially owing to the screening mechanism that operates inside halos such as the Milky Way to ensure that gravity tests in the solar system are satisfied. This opens up several decades in length scale and classes of galaxies at low redshift that can be exploited by surveys. While theoretical work on models of gravity is in the early stages, we can already identify new regimes that cosmological surveys could target to test gravity. These include: (i) a smallscale component that focuses on the interior and vicinity of galaxy and cluster halos, (ii) spectroscopy of low-redshift galaxies, especially galaxies smaller than the Milky Way, in environments that range from voids to clusters, and (iii) a programme of combining lensing and dynamical information, from imaging and spectroscopic surveys, respectively, on the same (or statistically identical) sample of galaxies.
Multiple-symbol differential detection of MPSK

A differential detection technique for MPSK (multiple-phase shift keying), which uses a multiple-symbol observation interval, is presented, and its performance is analyzed and simulated. The technique makes use of maximum-likelihood sequence estimation of the transmitted phases rather than symbol-by-symbol detection as in the conventional differential detection. Thus, the performance of this multiple-symbol detection scheme fills the gap between conventional (two-symbol observation) differentially coherent detection of MPSK and ideal coherent of MPSK with differential encoding. The amount of improvement gained over conventional differential detection depends on the number of phases M and the number of additional symbol intervals added to the observation. What is particularly interesting is that substantial performance improvement can be obtained for only one or two additional symbol intervals of observation. The analysis and simulation results presented are for uncoded MPSK. >
Anomalous reflection of a shock wave at a fluid interface

Several wave patterns can be produced by the interaction of a shock wave with a fluid interface. We focus on the case when the shock passes from a medium of high to low acoustic impedance. Curvature of either the shock front or contact causes the flow to bifurcate from a locally self-similar quasi-stationary shock diffraction, to an unsteady anomalous reflection. This process is analogous to the transition from a regular to a Mach reflection when the reflected wave is a rarefaction instead of a shock. These bifurcations have been incorporated into a front tracking code that provides an accurate description of wave interactions. Numerical results for two illustrative cases are described; a planar shock passing over a bubble, and an expanding shock impacting a planar contact.
Particle absorption by black holes and the generalized second law of thermodynamics

The change in entropy, Δ S , associated with the quasi-static absorption of a particle of energy e by a Schwarzschild black hole (ScBH) is approximately ( e / T )− s , where T is the Hawking temperature of the black hole and s is the entropy of the particle. Motivated by the statistical interpretation of entropy, it is proposed here that the absorption should be suppressed, but not forbidden, when Δ S S . A purely thermodynamic formulation of the probability for the absorption is obtained from the standard relationship between microstates and entropy. If Δ S ≫1 and s ≪ e / T , then the probability for the particle not to be absorbed is approximately exp[− e / T ], which is identical to the probability for quantum mechanical reflection by the horizon of an ScBH. The manifestation of quantum behaviours in the new probability function may intimate a fundamental physical unity between thermodynamics and quantum mechanics.
Silence, Death, and the Invisible Enemy: AIDS Activism and Social Movement “Newness”

Examining the dynamics and activities of the AIDS activist movement—here, through an analysis based on a participant-observation study of the AIDS Coalition to Unleash Power (ACT UP) in San Francisco—provides an opportunity to clarify issues on which social movements literature tends to be hazy. ACT UP mixes strategic action and material targets with expressive action and cultural targets; their cultural activity takes the form of boundary-crossing and the contesting of images. They often have difficulty distinguishing their targets, and are caught both denying and affirming that AIDS is a gay disease. I argue that these actions and dilemmas are best understood in the context of changed forms of domination, more and more an invisible and disembodied process of “normalization,” with the state gradually less directly involved. This argument not only explains the particulars of ACT UP's activism, but also poses challenges to theorizing on contemporary (“new”) social movements.
Understanding nucleic acids using synthetic chemistry

This Account describes work done in these laboratories that has used synthetic, physical organic, and biological chemistry to understand the roles played by the nucleobases, sugars, and phosphates of DNA in the molecular recognition processes central to genetics. The number of nucleobases has been increased from 4 to 12, generating an artificially expanded genetic information system. This system is used today in the clinic to monitor the levels of HIV and hepatitis C viruses in patients, helping to manage patient care. Work with uncharged phosphate replacements suggests that a repeating charge is a universal feature of genetic molecules operating in water and will be found in extraterrestrial life (if it is ever encountered). The use of ribose may reflect prebiotic processes in the presence of borate-containing minerals, which stabilize ribose formed from simple organic precursors. A new field, synthetic biology, is emerging on the basis of these experiments, where chemistry mimics biological processes as complicated as Darwinian evolution.
Health and Wellness Policy Ethics

This perspective is an ethical brief overview and examination of “wellness” policies in the modern workplace using practical examples and a general application of utilitarianism. Many employers are implementing policies that provide incentives to employees who lead a “healthy” lifestyle. The authors address how these policies could adversely affect “non-healthy” employees. There are a wide variety of ethical issues that impact wellness policies and practices in the workplace. The authors conclude that wellness programs can be ethical, while also providing a general reflective analysis of healthcare challenges in order to reflect on the externalities associated with such policies in the workplace.
Preparing the U.S. Health Community for Climate Change

In society's effort to address and prepare for climate change, the health community itself must ensure that it is prepared. Health personnel will require flexible and iterative action plans to address climate change at the individual, hospital, local health department, state, and national levels. This requires that health workers analyze the impact of climate change with a view to human health, and then formulate robust policy and demonstrate authentic leadership. In this review, we summarize the status of the health community's preparation for climate change and provide specific recommendations for action at each level. Although preparation status and recommendations vary, our observation is that it is not enough for public health and medical care agencies and departments to develop policies and advocate change. They have a direct responsibility to demonstrate substantive leadership.
The maximum speed of dynamical evolution

Abstract We discuss the problem of counting the maximum number of distinct states that an isolated physical system can pass through in a given period of time — its maximum speed of dynamical evolution. Previous analyses have given bounds in terms of ΔE, the standard deviation of the energy of the system; here we give a strict bound that depends only on E − E0, the system's average energy minus its ground state energy. We also discuss bounds on information processing rates implied by our bound on the speed of dynamical evolution. For example, adding 1 J of energy to a given computer can never increase its processing rate by more than about 3 × 1033 operations per second.
Corporate Reporting and the Internet: Vision, Reality, and Intervening Obstacles

The rapid evolution of Internet technology has created the ability to disseminate new information nearly instantaneously to a world‐wide audience. Many business and finance organisations have already applied this capability. Examples are real‐time stock quotes, on‐line news wires and e‐commerce.
Oscillatory three-phase flow reactor for studies of bi-phasic catalytic reactions

A multi-phase flow strategy, based on oscillatory motion of a bi-phasic slug within a fluorinated ethylene propylene (FEP) tubular reactor, under inert atmosphere, is designed and developed to address mixing and mass transfer limitations associated with continuous slug flow chemistry platforms for studies of bi-phasic catalytic reactions. The technique is exemplified with C–C and C–N Pd catalyzed coupling reactions.
The Deterrent Effect of Capital Punishment: An Analysis of Daily Homicide Counts

Abstract This article analyzes daily homicide data to address whether the occurrence of executions exerts a short-term deterrent effect. The data analyzed are drawn from computerized death certificates from California during the early 1960s, the last period during which frequent executions were carried out there. The analysis of data from one legal jurisdiction helps overcome criticisms of earlier studies based on data aggregated over executing and nonexecuting jurisdictions. Furthermore, the detailed information in the death certificates allows one to analyze the murders of victims of different race and sex separately, which in principle should allow one to detect possible race- or gender-specific effects too small to be discerned in aggregate data. Poisson and compound-Poisson regression models are estimated, to control for seasonal fluctuations and to measure the effect of executions on daily homicide counts. Two-week and four-week periods surrounding the dates on which executions took place are examin...
InSb charge-injection device imaging array

InSb CID arrays, in both 1 × 32 line and 16 × 24 two-dimensional format, have been successfully fabricated via a multilayer MIS processing technique. With the 1 × 32 line arrays, two-dimensional images were generated using a scanning mirror and a computer signal-conditioning technique. In this experiment the small temperature difference of a man's face was revealed. Two-dimensional, 16 × 24 area arrays have also been demonstrated in a staring mode by displaying real time raster-scanned IR images directly on a X-Y CRT monitor. The unprocessed IR video signal produced a sharp, clearly recognizable display with no sign of blooming, and exhibited excellent operating characteristics. Theoretical analysis showed that, at low sample rates, background limited performance (BLIP) can be obtained at background photon flux levels of as low as mid-1012photons/s . cm2. The dominant noise source, in this case, is the integrated dark current shot noise. For operation at high sample rates, however, the bandwidth-dependent noise sources limit the array performance and, thus, BLIP occurs at higher background levels. The analysis has been confirmed by measured data on line arrays, resulting in good agreement between the theoretical curve and the experimental data.
Examination of soil moisture retrieval using SIR-C radar data and a distributed hydrological model

A major objective of soil moisture-related hydrological research during NASA's SIR-C/X-SAR mission was to determine and compare soil moisture patterns within humid watersheds using SAR data, ground-based measurements, and hydrologic modeling. Currently available soil moisture inversion methods using active microwave data are only accurate when applied to bare and slightly vegetated surfaces. Moreover, as the surface dries down, the number of pixels that can provide estimated soil moisture by these radar inversion methods decreases, leading to less accuracy and confidence in the retrieved soil moisture fields at the watershed scale. The impact of these errors in microwave-derived soil moisture on hydrological modeling of vegetated watersheds has yet to be addressed. In this study a coupled water and energy balance model operating within a topographic framework is used to predict surface soil moisture for both bare and vegetated areas. In the first model run, the hydrological model is initialized using a standard baseflow approach, while in the second model run, soil moisture values derived from SIR-C radar data are used for initialization. The results, which compare favorably with ground measurements, demonstrate the utility of combining radar-derived surface soil moisture information with basin-scale hydrological modeling.
The Effect of Randomized School Admissions on Voter Participation

There is little causal evidence on the effect of economic and policy outcomes on voting behavior. This paper uses randomized outcomes from a school choice lottery to examine if lottery outcomes affect voting behavior in a school board election. We show that losing the lottery has no significant impact on overall voting behavior; however, among white families, those with above median income and prior voting history, lottery losers were significantly more likely to vote than lottery winners. Using propensity score methods, we compare the voting of lottery participants to similar families who did not participate in the lottery. We find that losing the school choice lottery caused an increase in voter turnout among whites, while winning the lottery had no effect relative to non-participants. Overall, our empirical results lend support to models of expressive and retrospective voting, where likely voters are motivated to vote by past negative policy outcomes.
Teaching experientially with the Madeline Hunter method: an application in a marketing research course

Due to concerns about the disparity of learning and the high nonresponse rates encountered by student marketing research teams working with sponsors, the author adopted the Hunter Method to restructure his course. This method requires the use of a model onto which students can map their learning via guided practice as well as independent practice. This approach allows student teams to select different topics, but they must use identical research objectives. The author claims that it levelizes learning, renders learning easier for students, and enhances instructor efficiency.
Enantioselective Syntheses of Heteroyohimbine Natural Products: A Unified Approach through Cooperative Catalysis.

Alstonine and serpentine are pentacyclic indoloquinolizidine alkaloids (referred to as “anhydronium bases”) containing three contiguous stereocenters. Each possesses interesting biological activity, with alstonine being the major component of a plant-based remedy to treat psychosis and other nervous system disorders. This work describes the enantioselective total syntheses of these natural products with a cooperative hydrogen bonding/enamine-catalyzed Michael addition as the key step.
Distributed link scheduling with constant overhead

This paper proposes a new class of simple, distributed algorithms for scheduling in wireless networks. The algorithms generate new schedules in a distributed manner via simple local changes to existing schedules. The class is parameterized by integers k\geq 1. We show that algorithm k of our class achieves k/(k+2) of the capacity region, for every k\geq 1. . The algorithms have small and constant worst-case overheads: in particular, algorithm k generates a new schedule using (a) time less than 4k+2 round-trip times between neighboring nodes in the network, and (b) at most three control transmissions by any given node, for any k. The control signals are explicitly specified, and face the same interference effects as normal data transmissions. Our class of distributed wireless scheduling algorithms are the first ones guaranteed to achieve any fixed fraction of the capacity region while using small and constant overheads that do not scale with network size. The parameter k explicitly captures the tradeoff between control overhead and scheduler throughput performance and provides a tuning knob protocol designers can use to harness this trade-off in practice.
An instrumentation technique for online analysis of multithreaded programs

This paper presents an automatic code instrumentation technique, based on multithreaded vector clocks, for extracting the causal partial order on relevant state update events from a running multithreaded program. This technique is used in a formal testing environment, not only to detect, but especially to predict safety errors in multithreaded programs. The prediction process consists of rigorously analyzing other potential executions that are consistent with the causal partial order: some of these can be erroneous despite the fact that the particular observed execution was successful. The technique has been implemented as part of a Java program analysis tool. Copyright © 2006 John Wiley & Sons, Ltd.
A double auction market: Teaching, experiment, and theory

A simultaneous double auction market with bid and offer cards was used in classes on the theory and history of money and financial institutions and occasionally in classes on the theory of games. The prime purpose in using this game was to teach the students how to construct process models of economic phenomena. The second purpose was to consider the properties of the double auction market. The third purpose was to interpret the experimental results and link them to theory.
Privacy, economics, and price discrimination on the Internet

The rapid erosion of privacy poses numerous puzzles. Why is it occurring, and why do people care about it? This paper proposes an explanation for many of these puzzles in terms of the increasing importance of price discrimination. Privacy appears to be declining largely in order to facilitate difierential pricing, which ofiers greater social and economic gains than auctions or shopping agents. The thesis of this paper is that what really motivates commercial organizations (even though they often do not realize it clearly themselves) is the growing incentive to price discriminate, coupled with the increasing ability to price discriminate. It is the same incentive that has led to the airline yield management system, with a complex and constantly changing array of prices. It is also the same incentive that led railroads to invent a variety of price and quality difierentiation schemes in the 19th century. Privacy intrusions serve to provide the information that allows sellers to determine buyers' willingness to pay. They also allow monitoring of usage, to ensure that arbitrage is not used to bypass discriminatory pricing.Economically, price discrimination is usually regarded as desirable, since it often increases the efficiency of the economy. That is why it is frequently promoted by governments, either through explicit mandates or through indirect means. On the other hand, price discrimination often arouses strong opposition from the public.There is no easy resolution to the conflict between sellers; incentives to price discriminate and buyers' resistance to such measures. The continuing tension between these two factors will have important consequences for the nature of the economy. It will also determine which technologies will be adopted widely. Governments will likely play an increasing role in controlling pricing, although their roles will continue to be ambiguous. Sellers are likely to rely to an even greater extent on techniques such as bundling that will allow them to extract more consumer surplus and also to conceal the extent of price discrimination. Micropayments and auctions are likely to play a smaller role than is often expected. In general, because of strong conflicting pressures, privacy is likely to prove an intractable problem that will be prominent on the the public agenda for the foreseeable future.
Prototype Supported Metal Cluster Catalysts: Ir4 and Ir6

The following is a review of the synthesis, chemistry, and catalytic properties of small, well-defined supported metal clusters, Ir4 and Ir6. These supported clusters are synthesized either by adsorption of ligated molecular iridium clusters with tetrahedral and octahedral frameworks, for Ir4 and Ir6, respectively, or by adsorption of single-iridium-atom complexes followed by treatment to form clusters on the supports. The most insightful characterizations of supported metal clusters have been carried out by infrared and X-ray absorption spectroscopies and aberration-corrected scanning transmission electron microscopy. Reactions of the supported clusters include ligand modifications and ligand removal, oxidative fragmentation, and migration leading to metal aggregation. Reactivities and catalytic properties of the clusters (e.g., for olefin hydrogenation) depend on the cluster size and the support (which acts as a ligand) and are distinct from those of supported particles that resemble bulk iridium. Transient spectroscopic data illustrate that the structures of the active species in ethylene hydrogenation catalysis switch reversibly from Ir4 to single-iridium-atom complexes in response to changes in the ethylene/H2 ratio in the gas phase. Density functional theory has been used to predict properties of these clusters, notably their ability to add hydrogen, and the agreement between theory and experiment is good. Recent advances in the characterization of supported Ir4 and Ir6 clusters have been crucial in the elucidation of their behavior, and these methods apply as well to the more complicated structures of industrial supported metal catalysts.
Conjugacy classes of non-translations in affine Weyl groups and applications to Hecke algebras

Let W be an Iwahori-Weyl group of a connected reductive group G over a non-archimedean local field. I prove that if w is an element of W that does not act on the corresponding apartment of G by a translation then one can apply to w a sequence of conjugations by simple reflections, each of which is length-preserving, resulting in an element w' for which there exists a simple reflection s such that l(sw's)>l(w'). Even for affine Weyl groups, a special case of Iwahori-Weyl groups and also an important subclass of Coxeter groups, this is a new fact about conjugacy classes. Further, there are implications for Iwahori-Hecke algebras H of G: one can use this fact to give dimension bounds on the "length-filtration" of the center Z(H), which can in turn be used to prove that suitable linearly-independent subsets of Z(H) are a basis.
Electron scattering mechanisms at polar GaN/AlGaN interfaces

We present recent results of calculations of charge transfer and electron mobilities in nominally undoped AlGaN/GaN heterostructures. It has previously been proposed that the two-dimensional electron gas (2-DEG) originates from donor- like defects on the surface of the AlGaN barrier. We have made detailed calculations of a model in which these defects are created under thermodynamic equilibrium at the growth temperature and show that the spontaneous and strain-induced piezoelectric fields in the AlGaN barrier enhance the formation of these defects. In calculating the low temperature electron mobility in these structures, we consider all the major scattering mechanisms including acoustic phonons, Coulomb scattering from charged centers, and alloy disorder scattering. The relative importance of the different scattering mechanisms depends strongly on the 2-DEG density. At densities smaller than about 2x1012cm-2, the mobility is limited by Coulomb scattering. At higher densities, alloy disorder scattering becomes the dominant electron scattering process. Finally, we have calculated the ratio of the transport to quantum lifetimes ((tau) t/(tau) q for various AlGaN/GaN heterostructures and find that the value of the ratio cannot be used to infer the nature of the dominant scattering mechanism, as is traditionally assumed.
Large-scale annotation of small-molecule libraries using public databases.

While many large publicly accessible databases provide excellent annotation for biological macromolecules, the same is not true for small chemical compounds. Commercial data sources also fail to encompass an annotation interface for large numbers of compounds and tend to be cost prohibitive to be widely available to biomedical researchers. Therefore, using annotation information for the selection of lead compounds from a modern day high-throughput screening (HTS) campaign presently occurs only under a very limited scale. The recent rapid expansion of the NIH PubChem database provides an opportunity to link existing biological databases with compound catalogs and provides relevant information that potentially could improve the information garnered from large-scale screening efforts. Using the 2.5 million compound collection at the Genomics Institute of the Novartis Research Foundation (GNF) as a model, we determined that ∼4% of the library contained compounds with potential annotation in such databases as ...
Efficient solution phase synthesis of 2-(N-acyl)-aminobenzimidazoles

Abstract An efficient solution phase protocol for the synthesis of 2-(N-acyl)-aminobenzimidazoles is reported. The 2-(N-acyl)-aminobenzimidazole ring system was assembled using SNAr reactions, nitro group reduction, acylthiourea formation and cyclization with EDC. The acyl protected 2-aminobenzimidazole derivatives were obtained in high yield and purity without purification of intermediates or final products. This reaction sequence eliminates the use of highly toxic cyanogen bromide, a reagent commonly used to prepare the 2-aminobenzimidazole ring system.
Bismuth compounds in organic synthesis. Synthesis of resorcinarenes using bismuth triflate

Abstract Bismuth triflate (5 mol%) smoothly catalyzes the condensation of aromatic and aliphatic aldehydes with resorcinol to give tetrameric cyclic products, resorcinarenes. With benzaldehyde, the product is obtained as a mixture of two diastereomers and the ratio of the diastereomers depends on reaction time. On the other hand, a single diastereomer is obtained with aliphatic aldehydes. The low toxicity and ease of handling of bismuth compounds coupled with fast reaction times make this method an attractive alternative to the existing methods for resorcinarene formation.
Rapidly mixing Gibbs sampling for a class of factor graphs using hierarchy width

Gibbs sampling on factor graphs is a widely used inference technique, which often produces good empirical results. Theoretical guarantees for its performance are weak: even for tree structured graphs, the mixing time of Gibbs may be exponential in the number of variables. To help understand the behavior of Gibbs sampling, we introduce a new (hyper)graph property, called hierarchy width. We show that under suitable conditions on the weights, bounded hierarchy width ensures polynomial mixing time. Our study of hierarchy width is in part motivated by a class of factor graph templates, hierarchical templates, which have bounded hierarchy width—regardless of the data used to instantiate them. We demonstrate a rich application from natural language processing in which Gibbs sampling provably mixes rapidly and achieves accuracy that exceeds human volunteers.
A Vanadium Chalcogenide Dicubane

The discovery of novel transition metal cubane clusters with different electron counts and topologies is of considerable importance due to the prevalence of this structure type in catalytic proteins. Here, we report the solvothermal synthesis and full characterization of [V7S8Cl2(en)8]Cl4 (en = ethylenediamine), the first early transition metal dicubane cluster. Electron paramagnetic resonance and magnetic susceptibility measurements show that the cluster has one unpaired electron localized on a single V4+, which according to DFT simulations is the central bridging vanadium. The remaining V3+ atoms feature significant metal–metal bonding.
Developmental and Individual Differences in Understanding of Fractions

We examined developmental and individual differences in 6th and 8th graders’ fraction arithmetic and overall mathematics achievement and related them to differences in understanding of fraction magnitudes, whole number division, executive functioning, and metacognitive judgments within a crosssectional design. Results indicated that the difference between low achieving and higher achieving children’s fraction arithmetic knowledge, already substantial in 6th grade, was much greater in 8th grade. The fraction arithmetic knowledge of low achieving children was similar in the 2 grades, whereas higher achieving children showed much greater knowledge in 8th than 6th grade, despite both groups having been in the same classrooms, using the same textbooks, and having the same teachers and classmates. Individual differences in both fraction arithmetic and mathematics achievement test scores were predicted by differences in fraction magnitude knowledge and whole number division, even after the contributions of reading achievement and executive functioning were statistically controlled. Instructional implications of the findings are discussed.
Interactive Proofs with Approximately Commuting Provers

The class \(\mathrm {MIP}^*\) of promise problems that can be decided through an interactive proof system with multiple entangled provers provides a complexity-theoretic framework for the exploration of the nonlocal properties of entanglement. Very little is known in terms of the power of this class. The only proposed approach for establishing upper bounds is based on a hierarchy of semidefinite programs introduced independently by Pironio et al. and Doherty et al. in 2006. This hierarchy converges to a value, the field-theoretic value, that is only known to coincide with the provers’ maximum success probability in a given proof system under a plausible but difficult mathematical conjecture, Connes’ embedding conjecture. No bounds on the rate of convergence are known.
Parts and wholes in face recognition

Are faces recognized using more holistic representations than other types of stimuli? Taking holistic representation to mean representation without an internal part structure, we interpret the available evidence on this issue and then design new empirical tests. Based on previous research, we reasoned that if a portion of an object corresponds to an explicitly represented part in a hierarchical visual representation, then when that portion is presented in isolation it will be identified relatively more easily than if it did not have the status of an explicitly represented part. The hypothesis that face recognition is holistic therefore predicts that a part of a face will be disproportionately more easily recognized in the whole face than as an isolated part, relative to recognition of the parts and wholes of other kinds of stimuli. This prediction was borne out in three experiments: subjects were more accurate at identifying the parts of faces, presented in the whole object, than they were at identifying ...
Statism in Russia: The implications for US–Russian relations

Abstract This essay seeks to identify and assess the general shift in Russian foreign policy thinking during Vladimir Putin’s presidency. The main thesis of this essay is that a general shift in Russian foreign policy had occurred during Putin’s presidency owing to the rise in Statist thinking. To substantiate the thesis, the author uses the State of the Nation addresses of Boris Yeltsin and Vladimir Putin to make a comparative analysis of the presidents’ foreign policy approaches. As demonstrated in the essay, the Russian foreign policy had experienced a dramatic influx of state power during Vladimir Putin’s presidency, which resulted in the relative quantitative and qualitative reduction of cooperative initiatives between the United States and Russia.
The Effect of Legal Status on Immigrant Wages and Occupational Skills

ABSTRACTNative and foreign-born workers with a high school degree or less education work in different types of occupations. This article exploits the 1986 Immigration Reform and Control Act to examine whether legal status causes immigrants to work in occupations that use skills similar to those of natives. Legal status decreases the manual skill intensity of immigrants’ occupations by about two percentiles. It increases communication skill intensity by a similar amount. This reduces the skill gap between Mexican-born and native-born American workers by 11–15%.
On the benefits of latent variable modeling for norming scales: The case of the Supports Intensity Scale – Children’s Version

Structural equation modeling (SEM) is a powerful and flexible analytic tool to model latent constructs and their relations with observed variables and other constructs. SEM applications offer advan...
A study of the factors that influence consumer attitudes toward beef products using the conjoint market analysis tool

This study utilizes an analysis technique commonly used in marketing, the conjoint analysis method, to examine the relative utilities of a set of beef steak characteristics considered by a national sample of 1,432 US consumers, as well as additional localized samples representing undergraduate students at a business college and in an animal science department. The analyses indicate that among all respondents, region of origin is by far the most important characteristic; this is followed by animal breed, traceability, animal feed, and beef quality. Alternatively, the cost of cut, farm ownership, the use (or nonuse) of growth promoters, and whether the product is guaranteed tender were the least important factors. Results for animal science undergraduates are similar to the aggregate results, except that these students emphasized beef quality at the expense of traceability and the nonuse of growth promoters. Business students also emphasized region of origin but then emphasized traceability and cost. The ideal steak for the national sample is from a locally produced, choice Angus fed a mixture of grain and grass that is traceable to the farm of origin. If the product was not produced locally, respondents indicated that their preferred production states are, in order from most to least preferred, Iowa, Texas, Nebraska, and Kansas.