cssi/SciSciGPT-SciSciNet huggingface dataset:
Physical and chemical tuning of two-dimensional transition metal dichalcogenides

The development of two-dimensional (2D) materials has been experiencing a renaissance since the adventure of graphene. Layered transition metal dichalcogenides (TMDs) are now playing increasingly important roles in both fundamental studies and technological applications due to their wide range of material properties from semiconductors, metals to superconductors. However, a material with fixed properties may not exhibit versatile applications. Due to the unique crystal structures, the physical and chemical properties of 2D TMDs can be effectively tuned through different strategies such as reducing dimensions, intercalation, heterostructure, alloying, and gating. With the flexible tuning of properties 2D TMDs become attractive candidates for a variety of applications including electronics, optoelectronics, catalysis, and energy.
Short stereoselective synthesis of α-substituted γ-lactams

A concise, stereoselective synthesis of α-substituted γ-lactams is reported. γ-Lactam scaffolds 2 and 3, possessing an Evans' chiral auxiliary and two types of N substituents, were successfully alkylated with different electrophiles to give α-substituted γ-lactams with reasonable diastereoselectivities. The use of a masked carboxymethyl function off the lactam nitrogen provided a convergent means to α-substituted γ-lactam dipeptide isosteres.
The South-to-North migration of women.

L'A. defie la sagesse conventionnelle selon laquelle, depuis l'interruption, dans les annees 1974, des politiques encourageant la migration de travail temporaire, la migration feminine a depasse la migration masculine. S'appuyant sur des donnees de Belgique, d'Allemagne, du Royaume-Uni et des Etats-Unis, il montre que la proportion de femmes dans la migration generale est plus importante dans le sens pays en voie de developpement / pays developpes. Les femmes surpassent en nombre les hommes en terme de migration nette. Chaque pays d'accueil a ses propres variations sur ces generalisations, les principales variables etant les politiques d'admission des pays d'accueil et l'etape dans l'histoire de la migration de la population expatriee
Susceptibility of Louisiana and Florida Populations of Spodoptera frugiperda (Lepidoptera: Noctuidae) to Pyramided Bt Corn Containing Genuity®Vt Double Pro™ and Smartstax™ Traits

ABSTRACT The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a target species of transgenic corn containing pyramided Bt genes in the United States. During 2011, a total of 149 F2 two-parental family lines were established using single-pairing of S. frugiperda collected from 3 locations in Louisiana and Florida. This study examined the susceptibility of these F2 two-parental family lines to 2 commonly used pyramided Bt corn traits, Genuity®VT Double Pro™ and Genuity®SmartStax™. Nine out of the 149 family lines showed less susceptibility to the leaf tissue of Genuity®VT Double Pro™ or Genuity®SmartStax plants. Larvae of these 9 family lines exhibited significant survivorship and growth on leaf tissue of the Bt corn plants. Two laboratory colonies were established from the F2 survivors of 2 of the 9 family lines. However, larvae from both colonies could not survive on whole plants of their corresponding Bt corn products in the greenhouse, suggesting these families were not resistant to the pyramided ...
Biomedical uses of Radiation

The types of radiation routinely used for medical diagnosis and treatment ranges from different kinds of electromagnetic radiation (radio, infrared, ultraviolet, X-ray) to ultrasound. Keeping pace with all the different methods, their specific advantages and their hidden dangers is almost impossible. Written by experienced experts mainly from the US, this handbook provides a comprehensive overview over the principles, advantages and potential risks of all radiation-based methods commonly used. Volume A describes the acting mechanisms for different types of radiation, volume B focuses on their clinical applications, the information collected by each method and their potential risks. An indispensable reference work for (radiation) physicians, biophysicists and medical engineers.
Semiparametric two-stage estimation of sample selection models subject to Tobit-type selection rules

A semlparametruz two-stage estimation method 1s proposed for the estimation of sample selectlon models which are subject to Toblt-type selectlon rules. With randomlzatlon restrIctIons on the disturbances of the model, all the regresslon coefficients m the model are, in general, ldentlfiable wIthout exclusion restrIctIons The proposed estimator is shown to be X/n-consistent and asymptotlcally normal. Some Monte Carlo results, to demonstrate Its limte sample performance, are provided.
Smooth metric measure spaces, quasi-Einstein metrics, and tractors

We introduce the tractor formalism from conformal geometry to the study of smooth metric measure spaces. In particular, this gives rise to a correspondence between quasi-Einstein metrics and parallel sections of certain tractor bundles. We use this formulation to give a sharp upper bound on the dimension of the vector space of quasi-Einstein metrics, providing a different perspective on some recent results of He, Petersen and Wylie.
Avoiding simplicity is complex

It is a trivial observation that every decidable set has strings of length n with Kolmogorov complexity log n + O(1) if it has any strings of length n at all. Things become much more interesting when one asks whether a similar property holds when one considers resource-bounded Kolmogorov complexity. This is the question considered here: Can a feasible set A avoid accepting strings of low resource-bounded Kolmogorov complexity, while still accepting some (or many) strings of length n?. More specifically, this paper deals with two notions of resource-bounded Kolmogorov complexity: Kt and KNt. The measure Kt was defined by Levin more than three decades ago and has been studied extensively since then. The measure KNt is a nondeterministic analog of Kt. For all strings x, Kt(x) K the two measures are polynomially related if and only if NEXP ⊆ EXP/poly [5]. Many longstanding open questions in complexity theory boil down to the question of whether there are sets in P that avoid all strings of low Kt complexity. For example, the EXP vs ZPP question is equivalent to (one version of) the question of whether avoiding simple strings is difficult: (EXP = ZPP if and only if there exist e > 0 and a "dense" set in P having no strings x with Kt(x) = |x|e [4]). Surprisingly, we are able to show unconditionally that avoiding simple strings (in the sense of KNt complexity) is difficult. Every dense set in NP ∩ co-NP contains infinitely many strings x such that KNt(x) ≤ |x|e for some e. The proof does not relativize. As an application, we are able to show that if E = NE, then accepting paths for nondeterministic exponential time machines can be found somewhat more quickly than the brute-force upper bound, if there are many accepting paths.
Symbiotic Origin of a Novel Actin Gene in the Cryptophyte Pyrenomonas helgolandii

Cryptophytes are photosynthetic protists that have acquired their plastids through the secondary symbiotic uptake of a red alga. A remarkable feature of cryptophytes is that they maintain a reduced form of the red algal nucleus, the nucleomorph, between the second and third plastid membranes (periplastidial compartment; PC). The nucleomorph is thought to be a transition state in the evolution of secondary plastids, with this genome ultimately being lost when photosynthesis comes under full control of the "host" nucleus (e.g., as in heterokonts, haptophytes, and euglenophytes). Genes presently found in the nucleomorph seem to be restricted to those involved in its own maintenance and to that of the plastid; other genes were lost as the endosymbiont was progressively reduced to its present state. Surprisingly, we found that the cryptophyte Pyrenomonas helgolandii possesses a novel type of actin gene that originated from the nucleomorph genome of the symbiont. Our results demonstrate for the first time that secondary symbionts can contribute genes to the host lineage which are unrelated to plastid function. These genes are akin to the products of gene duplication or lateral transfer and provide a source of evolutionary novelty that can significantly increase the genetic diversity of the host lineage. We postulate that this may be a common phenomenon in algae containing secondary plastids that has yet to be fully appreciated due to a dearth of evolutionary studies of nuclear genes in these taxa.
Holdups and efficiency with search frictions

A natural holdup problem arises in a market with search frictions: Firms have to make a range of investments before finding their employees, and larger investments translate into higher wages. In particular, when wages are determined by ex post bargaining, the equilibrium is always inefficient: Recognizing that capital-intensive production relations have to pay higher wages, firms reduce their investments. This can only be prevented by removing all the bargaining power from the workers, but this, in turn, depresses wages below their social product and creates excessive entry of firms. In contrast to this benchmark, we show that efficiency is achieved when firms post wages and workers can direct their search toward more attractive offers. This efficiency result generalizes to an environment with imperfect information where workers only observe a few of the equilibrium wage offers. We show that the underlying reason for efficiency is not wage posting per se, but the ability of workers to direct their search toward more capital-intensive jobs.
A Small cosmological constant from a large extra dimension

We propose a new approach to the Cosmological Constant Problem which makes essential use of an extra dimension. A model is presented in which the Standard Model vacuum energy “warps” the higher-dimensional spacetime while preserving 4D flatness. We argue that the strong curvature region of our solutions may effectively cut off the size of the extra dimension, thereby giving rise to macroscopic 4D gravity without a cosmological constant. In our model, the higher-dimensional gravity dynamics is treated classically with carefully chosen couplings. Our treatment of the Standard Model is however fully quantum field-theoretic, and the 4D flatness of our solutions is robust against Standard Model quantum loops and changes to Standard Model couplings.
Exploiting Social Network Structure for Person-to-Person Sentiment Analysis

Person-to-person evaluations are prevalent in all kinds of discourse and important for establishing reputations, building social bonds, and shaping public opinion. Such evaluations can be analyzed separately using signed social networks and textual sentiment analysis, but this misses the rich interactions between language and social context. To capture such interactions, we develop a model that predicts individual A ’s opinion of individual B by synthesizing information from the signed social network in which A and B are embedded with sentiment analysis of the evaluative texts relating A to B . We prove that this problem is NP-hard but can be relaxed to an efficiently solvable hinge-loss Markov random field, and we show that this implementation outperforms text-only and network-only versions in two very different datasets involving community-level decision-making: the Wikipedia Requests for Adminship corpus and the Convote U.S. Congressional speech corpus.
On the Cauchy Problem for Axi-Symmetric Vortex Rings

We consider the classical Cauchy problem for the three dimensional Navier–Stokes equation with the initial vorticity ω0 concentrated on a circle, or more generally, a linear combination of such data for circles with common axis of symmetry. We show that natural approximations of the problem obtained by smoothing the initial data satisfy good uniform estimates which enable us to conclude that the original problem with the singular initial distribution of vorticity has a solution. We impose no restriction on the size of the initial data.
A dual catalyst system provides the shortest pathway for L-menthol synthesis

We have demonstrated that a combination of enantiopure 2-diarylmethylpyrrolidines and heterogeneous Pd/BaSO4 is an efficient catalytic system for the asymmetric hydrogenation of citral, specifically, a mixture of E-citral and Z-citral in any ratio, and that citronellal is obtained with high enantioselectivity. This dual catalyst system provides a new and more economical route to L-menthol.
Compensatory mutations cause excess of antagonistic epistasis in RNA secondary structure folding

Background The rate at which fitness declines as an organism's genome accumulates random mutations is an important variable in several evolutionary theories. At an intuitive level, it might seem natural that random mutations should tend to interact synergistically, such that the rate of mean fitness decline accelerates as the number of random mutations is increased. However, in a number of recent studies, a prevalence of antagonistic epistasis (the tendency of multiple mutations to have a mitigating rather than reinforcing effect) has been observed.
Formation of a new bis-organocopper reagent from the reaction of 2,3-dichloropropene and highly active zero valent copper derived from a CuCN.2LiCl complex

Abstract Highly reactive zero valent copper derived from a CuCN·2LiCl complex reacts directly with 2,3-dichloropropene to yield a new bia-organocopper species containing both a nucleophilic allylic and vinylic moiety. This new bis-ogranocopper reagent undergoes selective one-pot addition to two different electrophiles in good to excellent yields.
Measurements with separated oscillatory fields and hydrogen masers

Descriptions are given of the methods of separated and successive oscillatory fields and of the atomic hydrogen maser. Their applications to precision spectroscopy of atoms and molecules are discussed along with specific examples of fundamental measurements best made with such devices. The applications of these methods to atomic clocks are also discussed. Cesium separated oscillatory fields atomic beam clocks are accurate to 10−13 and hydrogen masers are stable for several hours to 10−15. A discussion is given of fundamental experiments that require highly stable clocks, such as long base line radioastronomy, precise measurements of pulsar frequencies and stabilities, tests of the theories of relativity and accurate navigation both on the earth and in outer space.
Design considerations for piezoelectric polymer ultrasound transducers

The purpose of this paper is to present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design and front protection/matching layer design. The use of polymer wear-protection/quarter-wave matching layers is also discussed. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance.
Knowing in Practice: Enacting a Collective Capability in Distributed Organizing

In this paper, I outline a perspective on knowing in practice which highlights the essential role of human action in knowing how to get things done in complex organizational work. The perspective suggests that knowing is not a static embedded capability or stable disposition of actors, but rather an ongoing social accomplishment, constituted and reconstituted as actors engage the world in practice. In interpreting the findings of an empirical study conducted in a geographically dispersed hightech organization, I suggest that the competence to do global product development is both collective and distributed, grounded in the everyday practices of organizational members. I conclude by discussing some of the research implications of a perspective on organizational knowing in practice.
An Improved Synthesis Of 2-(Hydroxymethyl)Indene

(1996). AN IMPROVED SYNTHESIS OF 2-(HYDROXYMETHYL)INDENE. Organic Preparations and Procedures International: Vol. 28, No. 6, pp. 702-704.
Characterizing Truthful Multi-armed Bandit Mechanisms

We consider a multiround auction setting motivated by pay-per-click auctions for Internet advertising. In each round the auctioneer selects an advertiser and shows her ad, which is then either clicked or not. An advertiser derives value from clicks; the value of a click is her private information. Initially, neither the auctioneer nor the advertisers have any information about the likelihood of clicks on the advertisements. The auctioneer's goal is to design a (dominant strategies) truthful mechanism that (approximately) maximizes the social welfare. If the advertisers bid their true private values, our problem is equivalent to the multi-armed bandit problem, and thus can be viewed as a strategic version of the latter. In particular, for both problems the quality of an algorithm can be characterized by regret, the difference in social welfare between the algorithm and the benchmark which always selects the same “best” advertisement. We investigate how the design of multi-armed bandit algorithms is affecte...
Solid‐Phase Room‐Temperature Phosphorescence

Abstract Solid‐phase phosphorescence (SPP) has become an established approach for the trace analysis of organic compounds. More recently, SPP has been successfully applied to the trace analysis for inorganic species. In this mini review, initially a brief overview of SPP is given. Then the important aspects related to adsorption of the phosphors on the solid phase are discussed. In addition, the basic photophysical aspects of phosphorescence are presented. The physicochemical interactions in SPP, such as the rigidity of the solid phase, effects of oxygen and moisture, heavy‐atom salts, and temperature, are considered. Finally, several recent applications of SPP to both organic and inorganic compounds are discussed.
Gender and graduate economics education in the US

This paper reports on the findings of a survey of top economics graduate schools as they relate to women and men. The results provide strong evidence that at these top graduate schools, women graduate students are less integrated in their economic disciplines than are male graduate students. In the second part of the paper, this paper relates those findings to alternative theories as to why this is the case. This paper concludes by suggesting that the emphasis on theoretical studies in the current core of the graduate economics program can be seen as a type of hazing process that seems to have a significant cost since many women (and men) with great creative promise are discouraged from continuing in economics and do not benefit nearly as much as they would have from more policy-driven core courses.
Dissipationless mergers of elliptical galaxies and the evolution of the fundamental plane

We carry out numerical simulations of dissipationless major mergers of elliptical galaxies using initial galaxy models that consist of a dark matter halo and a stellar bulge with properties consistent with the observed fundamental plane. By varying the density profile of the dark matter halo [standard Navarro, Frenk & White (NFW) profile versus adiabatically contracted NFW profile], the global stellar to dark matter mass ratio and the orbit of the merging galaxies, we are able to assess the impact of each of these factors on the structure of the merger remnant. Our results indicate that the properties of the remnant bulge depend primarily on the angular momentum and energy of the orbit; for a cosmologically motivated orbit, the effective radius and velocity dispersion of the remnant bulge remain approximately on the fundamental plane. This indicates that the observed properties of elliptical galaxies are consistent with significant growth via late dissipationless mergers. We also find that the dark matter fraction within the effective radius of our remnants increases after the merger, consistent with the hypothesis that the tilt of the fundamental plane from the virial theorem is due to a varying dark matter fraction as a function of galaxy mass. Ke yw ords: methods: N-body simulations ‐ galaxies: evolution ‐ galaxies: fundamental parameters ‐ galaxies: structure ‐ dark matter.
Edge flows in the complete random-lengths network

Consider the complete n-vertex graph whose edge-lengths are independent exponentially distributed random variables. Simultaneously for each pair of vertices, put a constant flow between them along the shortest path. Each edge gets some random total flow. In the n→∞limit we find explicitly the empirical distribution of these edge-flows, suitably normalized. © 2010 Wiley Periodicals, Inc. Random Struct. Alg., 2010
Color Subspaces as Photometric Invariants

Complex reflectance phenomena such as specular reflections confound many vision problems since they produce image `features' that do not correspond directly to intrinsic surface properties such as shape and spectral reflectance. A common approach to mitigate these effects is to explore functions of an image that are invariant to these photometric events. In this paper we describe a class of such invariants that result from exploiting color information in images of dichromatic surfaces. These invariants are derived from illuminant-dependent `subspaces' of RGB color space, and they enable the application of Lambertian-based vision techniques to a broad class of specular, non-Lambertian scenes. Using implementations of recent algorithms taken from the literature, we demonstrate the practical utility of these invariants for a wide variety of applications, including stereo, shape from shading, photometric stereo, material-based segmentation, and motion estimation.
On the rectification of vibratory motion

The author establishes a theoretical framework for analyzing and classifying actuators which generate their output by rectifying small-amplitude mechanical vibrations such as might be generated by piezoelectric elements. These ideas are of interest when designing for microfabrication because motors based on these principles: (1) can generate translational output directly without use of rotary bearings; (2) appear to be scalable over several orders of magnitude of the length scale; and (3) appear to be capable of generating mechanical power proportional to driving frequency over several orders of magnitude of frequency. Achieving this performance is dependent on being able to fabricate features, or at least control surface irregularities, on the scale v/w where v is the velocity of the actuator and w is the operating frequency. >
On the Convergence Rates of Some Adaptive Markov Chain Monte Carlo Algorithms

This paper studies the mixing time of certain adaptive Markov Chain Monte Carlo algorithms. Under some regularity conditions, we show that the convergence rate of Importance Resampling MCMC algorithm, measured in terms of the total variation distance is O(n 1 ). By means of an example, we establish that in general, this algorithm does not converge at a faster rate. We also study the interacting tempering algorithm, a simplied version of Equi-Energy sampler, and establish that its mixing time is of order O(n 1=2 ).
Upper bounds for maximally greedy binary search trees

At SODA 2009, Demaine et al. presented a novel connection between binary search trees (BSTs) and subsets of points on the plane. This connection was independently discovered by Derryberry et al. As part of their results, Demaine et al. considered GREEDYFUTURE, an offline BST algorithm that greedily rearranges the search path to minimize the cost of future searches. They showed that GREEDYFUTURE is actually an online algorithm in their geometric view, and that there is a way to turn GREEDYFUTURE into an online BST algorithm with only a constant factor increase in total search cost. Demaine et al. conjectured this algorithm was dynamically optimal, but no upper bounds were given in their paper. We prove the first non-trivial upper bounds for the cost of search operations using GREEDYFUTURE including giving an access lemma similar to that found in Sleator and Tarjan's classic paper on splay trees.
Information and sorting in the market for obstetrical services

Using a statistical model and a partial equilibrium economic search model, we develop a methodology for appraising the value of consumer information about the quality of health care providers and apply it to information about physicians' predispositions to perform cesarean section deliveries. There are three primary results. First, information's value is roughly proportional to a simple statistical metric of its accuracy; the constant of proportionality can be imputed from knowledge of consumer search methods and consumer preferences. Second, the function governing the production of information from data 'inputs' can have surprising economic properties, such as economies of scale, that usefully inform the efficient production of consumer information. These properties are robust even when the value of information cannot be precisely determined. Third, information's value is enhanced by the way physicians are sorted into hospitals but greatly attenuated by the presence of other dimensions of physician heterogeneity. Under plausible assumptions, the value of information in our empirical application is small enough that it is not surprising that consumers do not utilize it when selecting a physician.
ALKALI DURABILITY OF OXYNITRIDE GLASS FIBERS

Oxynitride glass fibers were drawn from the melt in N2 atmospheres. The fibers were tested for their alkali durability in 10% NaOH at 96°C for 6 h. The durability is reported as weight loss in mg/cm2. The photomicrographs of the fibers before and after testing are presented. Calcium silicate oxynitride fibers have good durability because of a protective surface layer of Ca(OH)2. Yttria-containing glasses have the best durability among the compositions reported here.
A picture tells a thousand words-About you! User interest profiling from user generated visual content

Inference of online social network users' attributes and interests has been an active research topic. Accurate identification of users' attributes and interests is crucial for improving the performance of personalization and recommender systems. Most of the existing works have focused on textual content generated by the users and have successfully used it for predicting users' interests and other identifying attributes. However, little attention has been paid to user generated visual content (images) that is becoming increasingly popular and pervasive in recent times. We posit that images posted by users on online social networks are a reflection of topics they are interested in and propose an approach to infer user attributes from images posted by them. We analyze the content of individual images and then aggregate the image-level knowledge to infer user-level interest distribution. We employ image-level similarity to propagate the label information between images, as well as utilize the image category information derived from the user created organization structure to further propagate the category-level knowledge for all images. A large scale social network dataset of 1.5+ million images created from Pinterest is used for evaluation and the experimental results demonstrate the effectiveness of our proposed approach. HighlightsWe propose to solve user profiling using visual content.We propose a group-level label propagation for user-level interest estimation.A large scale dataset has been built for user profiling.
An Inequality for Nearly Log-Concave Distributions With Applications to Learning

We prove that given a nearly log-concave distribution, in any partition of the space to two well separated sets, the measure of the points that do not belong to these sets is large. We apply this isoperimetric inequality to derive lower bounds on the generalization error in learning. We further consider regression problems and show that if the inputs and outputs are sampled from a nearly log-concave distribution, the measure of points for which the prediction is wrong by more than epsi0 and less than epsi1 is (roughly) linear in epsi1-epsi0, as long as epsi0 is not too small, and epsi1 not too large. We also show that when the data are sampled from a nearly log-concave distribution, the margin cannot be large in a strong probabilistic sense
Intrinsic resistance to JAK2 inhibition in myelofibrosis

Purpose: Recent results have shown that myeloproliferative neoplasms (MPN) are strongly associated with constitutive activation of the Janus-activated kinase (JAK)2 tyrosine kinase. However, JAK2 inhibitors currently approved or under development for treating myeloproliferative neoplasms do not selectively deplete the malignant clone, and the inhibition of activity of the drug target (JAK2) has not been rigorously evaluated in the clinical studies. Therefore, in this study we developed an in vitro assay to gain insight into how effectively JAK2 activity is inhibited in the samples of patients. Experimental Design: We treated primary cells from normal donors and patients with MPN with JAK2 inhibitors and measured phosphorylation of downstream targets STAT5 and STAT3 by flow cytometry. Obtained results were next correlated with JAK2 V617F allele burden and plasma cytokine level. Results: We observed a dose-dependent decrease in pSTAT5 and pSTAT3 in ex vivo treated granulocytes. However, phosphorylation of STAT3 and STAT5 in cells from patients with myelofibrosis was significantly less inhibited when compared with cells from patients with polycythemia vera, essential thrombocythemia, and normal donors. Sensitivity to inhibition did not correlate with JAK2 V617F clonal burden. Mixing studies using plasma from patients with myelofibrosis did not transfer resistance to sensitive cells. Likewise, no single cytokine measured seemed to account for the observed pattern of resistance. Conclusions: Taken together, these observations suggest that there are cell intrinsic mechanisms that define a priori resistance to JAK2 inhibition in myelofibrosis, and the lesion is localized upstream of STAT3 and STAT5. Clin Cancer Res; 19(7); 1729–39. ©2013 AACR .
Magnetic breakdown in twisted bilayer graphene

We consider magnetic breakdown in twisted bilayer graphene where electrons may hop between semiclassical $k$-space trajectories in different layers. These trajectories within a doubled Brillouin zone (BZ) constitute a network in which an $S$ matrix at each saddle point (SP) is used to model interlayer tunneling. Although semiclassical orbits at a given energy all have the same shape, we find that the doubled BZ supports two distinct quantization conditions above the SP, versus only one below it, yielding a more intricate spectrum. Possible experimental signatures are discussed.
The structural cause of file size distributions

We propose a user model that explains the shape of the distribution of file sizes in local file systems and in the World Wide Web. We examine evidence from 562 file systems, 38 Web clients and 6 Web servers, and find that this model is an accurate description of these systems. We compare this model to an alternative that has been proposed, the Pareto model. Our results cast doubt on the widespread view that the distribution of file sizes is long-tailed; we discuss the implications of this conclusion for proposed explanations of self-similarity in the Internet.
Pursuit and Synchronization in Hydrodynamic Dipoles

We study theoretically the behavior of a class of hydrodynamic dipoles. This study is motivated by recent experiments on synthetic and biological swimmers in microfluidic Hele-Shaw type geometries. Under such confinement, a swimmer’s hydrodynamic signature is that of a potential source dipole, and the long-range interactions among swimmers are obtained from the superposition of dipole singularities. Here, we recall the equations governing the positions and orientations of interacting asymmetric swimmers in doubly periodic domains and focus on the dynamics of pairs of swimmers. We obtain two families of “relative equilibria”-type solutions that correspond to pursuit and synchronization of the two swimmers. Interestingly, the pursuit mode is stable for large-tail swimmers, whereas the synchronization mode is stable for large-head swimmers. These results have profound implications on the collective behavior reported in several recent studies on populations of confined microswimmers.
Synthesis of allyl selenides by palladium-catalyzed decarboxylative coupling

This communication details the Pd-catalyzed decarboxylation of selenocarbonates; use of a chiral nonracemic catalyst affords enantioenriched allyl selenides which undergo stereospecific [2,3]-sigmatropic rearrangements to form enantioenriched allylic amines and chlorides.
Ideas and Growth

This paper introduces and partially develops a new model of endogenous technological change, viewed as the product of a class of problem-solving producers. The model, based on earlier work by Eaton and Kortum, is built up from the premise that all knowledge resides in the head of some individual person and the knowledge of a firm, or economy, or any group of people is simply the knowledge of the individuals that comprise it. The model is applied to an economy with a cohort structure. A calibration of the model using cross-section earnings data, in addition to aggregate GDP growth, is considered. What is it about modern capitalist economies that allows them, in contrast to all earlier societies, to generate sustained growth in productivity and living standards? It is widely agreed that the productivity growth of the industrialized economies is mainly an ongoing intellectual achievement, a sustained flow of new ideas. Are these ideas the achievements of a few geniuses, Newton, Beethoven and a handful of others, viewed as external to the activities of ordinary people? Are they the product of a specialized research sector, engaged in the invention of patent-protected processes over which they have monopoly rights? Both images are based on important features of reality and both have inspired interesting growth theories, but neither seems to me central. What is central, I believe, is the fact that the industrial revolution involved the emergence (or rapid expansion) of a class of educated people, thousands - now many millions - of people who spend entire careers exchanging ideas, solving work-related problems, generating new knowledge. In this paper I introduce and partially develop a new model of technological change, viewed as the product of a class of problem-solving producers. The model is built up from the premise that all knowledge resides in the head of some individual person, so that the knowledge of a firm, or economy, or any group of people is simply a list of the knowledge of its members. A main feature of the model will be the social or reciprocal character of intellectual activity: Each person gains from the knowledge of the people around him; his ideas in turn stimulate others.1 As we will see, this idea is very flexible, but to develop it we need to have a tractable mathematical idealization of an individual's knowledge, of the relation of this knowledge
ON GENERATORS OF ARITHMETIC GROUPS OVER FUNCTION FIELDS

Let F = &#x1d53d;q(T) be the field of rational functions with &#x1d53d;q-coefficients, and A = &#x1d53d;q[T] be the subring of polynomials. Let D be a division quaternion algebra over F which is split at 1/T. For certain A-orders in D we find explicit finite sets generating their groups of units.
A rigid irregular connection on the projective line

In this paper we construct a connection ∇ on the trivial G-bundle on P 1 for any simple complex algebraic group G, which is regular outside of the points 0 and ∞, has a regular singularity at the point 0, with principal unipotent monodromy, and has an irregular singularity at the point ∞, with slope 1/h, the reciprocal of the Coxeter number of G. The connection ∇, which admits the structure of an oper in the sense of Beilinson and Drinfeld, appears to be the characteristic 0 counterpart of a hypothetical family of l-adic representations, which should parametrize a specific automorphic representation under the global Langlands correspondence. These l- adic representations, and their characteristic 0 counterparts, have been constructed in some cases by Deligne and Katz. Our connection is constructed uniformly for any simple algebraic group, and characterized using the formalism of opers. It provides an example of the geometric Langlands correspondence with wild ramification. We compute the de Rham cohomology of our connection with values in a representation V of G, and describe the differential Galois group of ∇ as a subgroup of G.
Why the Parts Are Better (or Worse) Than the Whole The Unique-Attributes Hypothesis

People tend to rate members of a positive group (e.g., best friends) as superior to the average of that group and members of a negative group (e.g., worst enemies) as inferior to the average of that group. Five experiments tested a new theoretical account of these nonselective superiority and inferiority biases. According to this account, a member’s unique attribute (the dimension distinguishing that member positively or negatively from other group members) is used as the standard for comparing that member with other group members. The experimental results supported this hypothesis. When participants compared a randomly selected popular or unpopular vacation destination with other destinations, the target destination’s unique attribute was more accessible than its nonunique attributes (Experiments 1–4), and a popular destination was judged less above average if one of its nonunique attributes was the salient comparison standard (Experiment 4). In addition, the unique attribute was used as the comparison s...
Free energy simulations: Applications to the study of liquid water, hydrophobic interactions and solvent effects on conformational stability

Free energy simulations using the Metropolis Monte Carlo method and the coupling parameter approach with umbrella sampling are described for several problems of interest in structural biochemistry; the liquid water, the hydrophobic interaction of alkyl and phenyl groups in water and solvent effects on the conformational stability of the alanine dipeptide and the dimethyl phosphate anion in water. Proximity analysis of results is employed to identify stabilizing factors. Implications of result with respect to the structural chemistry of proteins and nucleic acids is considered.
The Institutional Environment for Telecommunications Investment

This paper demonstrates that a structurally derived, internationally comparable index of checks and balances on executive discretion created by variation in political structures and party systems affects relative rates of basic telecommunications infrastructure deployment in 147 countries during the period 1960‐1994. Models of infrastructure investment that omit the political characteristics of a prospective host country confound countries whose economic and demographic characteristics point to rapid demand growth for infrastructure services with those that create a potential trap for investors due to a higher probability of arbitrary change in the policy environment. The econometric analysis exploits both cross-sectional and temporal variation in the panel. A robust covariance-matrix estimator based on that developed by Newey and West is used to compute valid standard errors in the presence of heteroskedasticity and within unit-serial correlation, two common characteristics in the error-term structure of panel datasets.
Recent developments in robust microporous porphyrin solids

A review of the recent literature is presented which assesses the development of robust microporous porphyrin framework solids and their potential to perform selective sorption or heterogeneous shape- or size-selective catalysis. The review focuses only on those porphyrin solids whose porosity is robust, i.e. whose framework remains after the removal of solvates, as determined by thermal gravimetric analysis (TGA), X-ray powder diffraction (XRD), or gas adsorption studies. Eleven such robust porphyrin framework solids are presented. Copyright © 2004 Society of Porphyrins & Phthalocyanines.
Predicting Fixation Tendencies of the H3N2 Influenza Virus by Free Energy Calculation

The influenza virus evolves to escape from immune system antibodies that bind to it. We used free energy calculations with Einstein crystals as reference states to calculate the difference of antibody binding free energy (ΔΔG) induced by amino acid substitution at each position in epitope B of the H3N2 influenza hemagglutinin, the key target for antibodies. A substitution with a positive ΔΔG value decreases the antibody binding constant and increases viral fitness. On average, an uncharged to charged amino acid substitution generates the highest ΔΔG values. Also, on average, substitutions between small amino acids generate ΔΔG values near zero. The 21 sites in epitope B have varying expected free energy differences for a random substitution. Historical amino acid substitutions in epitope B for the A/Aichi/2/1968 strain of influenza A show that most fixed and temporarily circulating substitutions generate positive ΔΔG values. We propose that the observed pattern of H3N2 virus evolution is affected by the f...
Clean Care is Safer Care: the first global challenge of the WHO World Alliance for Patient Safety.

Dr. Pittet is from the Global Patient Safety Challenge, WHO World Alliance for Patient Safety; and Dr. Donaldson is from the WHO World Alliance for Patient Safety, WHO Headquarters, Geneva, Switzerland. Address reprint requests to Didier Pittet, MD, MS, Director, Infection Control Programme, University of Geneva Hospitals, 24 rue Micheli-du-Crest, 1211 Geneva-14, Switzerland. didier.pittet@hcuge.ch © World Health Organization [2005]. All rights reserved. The World Health Organization has granted SLACK Incorporated permission for the reproduction of this article. The authors thank the group of international experts and WHO members who worked to the development of the Global Patient Safety Challenge, in particular for their participation to the two international WHO Consultations, review of the available scientific evidence, writing of the WHO draft Guidelines on Hand Hygiene in Health Care, and fostering discussion among authors and members of the different task forces and working groups. The complete list of participants in the development of the guidelines documents is available at www.who.int/patientsafety/events/05/27_AprilParticipantList.pdf (accessed August 8, 2005). They also thank the patient safety team and other WHO staff from all the departments involved at HQ and in the regional offices for their work, the members of the Infection Control Programme at the University of Geneva Hospitals, and Rosemary Sudan for providing editorial assistance and outstanding support. For further information on the World Alliance or the Global Patient Safety Challenge, go to www.who.int/patientsafety/en (accessed August 8, 2005). Clean Care is Safer Care: The First Global Challenge of the WHO World Alliance for Patient Safety
Urban Neighborhood Context and Change in Depressive Symptoms in Late Life

IN 2007, Aneshensel et al. (2007) reported statistically significant variation in depressive symptoms across neighborhoods for a national sample of urban older adults. Although these differences were associated with living in a socioeconomically disadvantaged neighborhood, they proved to be entirely compositional in nature—due to the individual disadvantage of the persons comprising the neighborhoods. These findings are consistent with some other studies of older adults (e.g., Hybels et al., 2006; La Gory & Fitzpatrick, 1992) but inconsistent with still others that find neighborhood effects that persist net of individual characteristics (e.g., Kubzansky et al., 2005; Ostir, Eschbach, Markides, & Goodwin, 2003). At least some of these discrepancies are likely methodological because extant studies differ widely in samples, methods, measures, and analytic techniques. There are good reasons to expect that as adults age, they become increasingly vulnerable to the “press” of their neighborhood environments (Lawton, 1982). Glass and Balfour (2003) describe four mechanisms of greater vulnerability: longer duration of exposure; increased biological, psychological, and cognitive vulnerability; changing patterns of spatial use; and reliance on community sources of social integration. Cagney, Browning, and Wen (2005) add that neighborhood is especially consequential to older persons who age in place. Given these compelling reasons for expecting neighborhood effects and the inconsistent findings of previous studies, an additional examination of this topic is warranted. An overlooked factor is the cross-sectional design of these studies, which limits inferences about any causal impact of neighborhood. In this paper, we extend the Aneshensel et al. (2007) analysis, using the same sample, methodology, and analytic techniques, to ask whether neighborhood context significantly influences change over time in late-life depressive symptoms. This longitudinal design is a major strength because the unmeasured influences of unspecified etiologic factors that occurred prior to baseline are partially controlled statistically via the inclusion of baseline values of depressive symptoms, enhancing internal validity. This feature is particularly important for older persons for whom there is a lifetime accumulation at baseline of individual-level etiologic factors that may obscure the contemporaneous impact of neighborhood-level factors. Thus, the present analysis is a more sensitive test of the impact of neighborhood context than previous cross-sectional analyses.
Identifying and developing curricula in software engineering

One basis for developing an education program is the recognition of a continuing need for a certain class of professionals in our society.
Locating histories of crime: a bibliographical study

This article aims to assist both criminologists wishing to access historical work in their particular subfields and historians coming to the history of crime for the first time by providing a guide to the ways in which material on the history of crime and criminal justice can be most easily accessed. It reviews introductory texts, existing printed bibliographies and important works whose bibliographies offer good starting points. It then looks at specialist journals and IT-based sources before pinpointing briefly a few works that may provide inspiration as well as information. It focuses primarily on England but also suggests ways into the wider literature.
Emulating a gravity model to infer the spatiotemporal dynamics of an infectious disease

Extremely contagious, acute, immunizing childhood infections like measles exhibit spatiotemporal dynamics that depend on the nature of spatial contagion and spatiotemporal variations in population structure and demography. We study a metapopulation model for regional measles dynamics that uses a gravity coupling model and a time series susceptible-infected-recovered (TSIR) model for local dynamics. Standard maximum likelihood or Bayesian inference for this model is infeasible as there are potentially tens of thousands of latent variables in the model and each evaluation of the likelihood is expensive. We develop an ecient discretized Markov chain Monte Carlo (MCMC)
Enantioselective Construction of α-Quaternary Cyclobutanones by Catalytic Asymmetric Allylic Alkylation

No strain, no gain! The first transition metal-catalyzed enantioselective α-alkylation of cyclobutanones is reported. This method employs palladium catalysis and an electron-deficient PHOX-type ligand to afford all-carbon α-quaternary cyclobutanones in good to excellent yields and enantioselectivities (see scheme).