cssi/SciSciGPT-SciSciNet huggingface dataset:
Partial Cu occupancy in uranium copper diantimonide, UCu0.60(4))Sb2.

The title compound, UCu0.60(4)Sb2, crystallizes in the tetragonal space group P4/nmm. The U atom and one independent Sb atom have 4mm site symmetry, whereas the Cu atom and the other Sb atom have 42m site symmetry. Zigzag USb sheets stack perpendicular to the c axis. These sheets are separated by square-planar nets of Sb atoms and Cu atoms. The length of the a axis for UCuxSb2 is invariant to x, whereas there is a linear relationship between Cu occupancy and the length of the c axis (following Vegard’s Law) that holds for x between 0 and 1. This is explained in terms of the crystal structure.
REX: recursive, delta-based data-centric computation

In today's Web and social network environments, query workloads include ad hoc and OLAP queries, as well as iterative algorithms that analyze data relationships (e.g., link analysis, clustering, learning). Modern DBMSs support ad hoc and OLAP queries, but most are not robust enough to scale to large clusters. Conversely, "cloud" platforms like MapReduce execute chains of batch tasks across clusters in a fault tolerant way, but have too much overhead to support ad hoc queries.Moreover, both classes of platform incur significant overhead in executing iterative data analysis algorithms. Most such iterative algorithms repeatedly refine portions of their answers, until some convergence criterion is reached. However, general cloud platforms typically must reprocess all data in each step. DBMSs that support recursive SQL are more efficient in that they propagate only the changes in each step --- but they still accumulate each iteration's state, even if it is no longer useful. User-defined functions are also typically harder to write for DBMSs than for cloud platforms.We seek to unify the strengths of both styles of platforms, with a focus on supporting iterative computations in which changes, in the form of deltas, are propagated from iteration to iteration, and state is efficiently updated in an extensible way. We present a programming model oriented around deltas, describe how we execute and optimize such programs in our REX runtime system, and validate that our platform also handles failures gracefully. We experimentally validate our techniques, and show speedups over the competing methods ranging from 2.5 to nearly 100 times.
The theory and practice of high-resolution scanning electron microscopy

Abstract Recent advances in instrumentation have produced the first commercial examples of what can justifiably be called high-resolution scanning electron microscopes. The key components of such instruments are a cold field emission gun, a small-gap immersion probe-forming lens, and a clean dry-pumped vacuum. The performance of these microscopes is characterized by several major features including a spatial resolution, in secondary electron mode on solid specimens, which can exceed 1 nm on a routine basis; an incident probe current density of the order of 10 6 A/cm 2 ; and the ability to maintain these levels of performance over an accelerating voltage range of from 1 to 30 keV. This combination of high resolution, high probe current, low contamination and flexible electron-optical conditions provides many new opportunities for the application of the SEM to materials science, physics, and the life sciences.
Confinement studies in lattice QCD

Abstract We describe the current search for confinement mechanisms in lattice QCD. We report on a recent derivation of a lattice Ehrenfest–Maxwell relation for the Abelian projection of SU(2) lattice gauge theory. This gives a precise lattice definition of field strength and electric current due to static sources, charged dynamical fields, gauge fixing and ghosts. In the maximal Abelian gauge the electric charge is anti-screened analogously to the non-Abelian charge.
Electroweak Strings: A Progress Report

I describe the string solutions in the standard electroweak model and argue that they may be stabilized by quark, lepton or other bound states. I then reinterpret the sphaleron in terms of electroweak strings and show that it can be viewed as a loop of W-string or a segment of Z-string. (Talk presented at Texas/Pascos 1992 at Berkeley.)
Tracking Multiple Targets Simultaneously with a Phased Array Radar

A new technique is described by which radar tracks can be established and maintained in a dense multitarget environment. These targets may fly in formation, maneuver relative to each other, or be on crossing paths. They may fade and reappear, lose their resolution, or become resolved. If the formation members move apart, the formation track is split into separate tracks. Typical requirements for a formation tracking system are stated, followed by a discussion of the principles on which this design is based. The same logic applies both to single targets and to forma. tions. Finally, results from field tests are presented.
Computational modeling of brain tumors: discrete, continuum or hybrid?

In spite of all efforts, patients diagnosed with highly malignant brain tumors (gliomas), continue to face a grim prognosis. Achieving significant therapeutic advances will also require a more detailed quantitative understanding of the dynamic interactions among tumor cells, and between these cells and their biological microenvironment. Data-driven computational brain tumor models have the potential to provide experimental tumor biologists with such quantitative and cost-efficient tools to generate and test hypotheses on tumor progression, and to infer fundamental operating principles governing bidirectional signal propagation in multicellular cancer systems. This review highlights the modeling objectives of and challenges with developing such in silicobrain tumor models by outlining two distinct computational approaches: discrete and continuum, each with representative examples. Future directions of this integrative computational neuro-oncology field, such as hybrid multiscale multiresolution modeling are discussed.
Bias Crime Motivation: A Study of Hate Crime and Offender Neutralization Techniques Used Against the Amish

This research examines hate crimes against the Amish with a particular focus on offender neutralization techniques that are used after the offenses have been committed to justify and/or rationalize...
Mesoscopic thermal transport through a weak link

We consider mesoscopic thermal transport between two bulkdielectrics joined by a narrow wire or weak mechanical link. In the ‘‘tunneling’’ regime where the phonon transmission probability through the link is small and the thermal conductance is much less than pk 2T=6_; the thermal current is determined by a product of the local vibrational spectral densities of the two bodies. We derive an expression for the thermal current that is a thermal analog of the wellknown formula for the electrical current through a tunneling barrier. r 2002 Elsevier Science B.V. All rights reserved.
High-performance pure permanent-magnet undulators

Abstract Pure permanent-magnet (PM) undulator designs that can match or exceed the on-axis field of PM hybrids are presented. Linearity and superposition of fields allows us to construct undulators with optimized performance for both FEL and synchrotron-radiation applications. Examples and performance data are given.
Effect of Low-Frequency Modulation on Lubrication of Chip-Tool Interface in Machining

A study has been made of the effect of an externally imposed, low-frequency modulation (≤100 Hz) on the action of a fluid in machining. It is shown that in conventional machining, fluid action in terms of lubrication is essentially confined to the edges of the chip-tool contact along the tool rake face, with little or no change in the friction condition over much of this face. However, the effectiveness of the lubricating action is significantly enhanced when a controlled low-frequency modulation of sufficient amplitude, such as to break the chip-tool contact, is imposed in the direction of cutting. Measurements show that the friction coefficient between tool and chip is reduced by a factor of up to three in the presence of such a modulation. The extent of the secondary deformation zone in the chip material close to the rake face is also significantly reduced. Direct observations of the tool rake face show that when the modulation is applied, the fluid penetrates into much of the intimate contact region between chip and tool.
AuCl3-Catalyzed Synthesis of Highly Substituted Furans from 2-(1-Alkynyl)-2-alken-1-ones

Highly substituted furans have been synthesized by the reaction of 2-(1-alkynyl)-2-alken-1-ones and various nucleophiles under very mild reaction conditions in good to excellent yields. Gold and some other transition metals are efficient catalysts for this reaction.
Cholinergic rebound in neuroleptic withdrawal syndromes.

A variety of symptoms, including headache, diarrhea, perspiration, restlessness, nausea, and vomiting, have been reported occurring after the abrupt withdrawal of neuroleptic medication}') These withdrawal syndromes are speculated to be partly related to the autonomic activity ofthe withdrawn antipsychotic drug and/or the concomitantly administered anticholinergic medica­ tion. They are exclusive of the range of symptoms considered part of the tardive or persistent dyskinesia syndromes, and ofthe psychopathologic symptoms that may return upon neuroleptic withdrawal...· s They have been characterized as "medical effects" by Lacour­ siere,' and they may be mistaken for unrelated medical illness, as the following case illustrates.
Velocity distributions and annual-modulation signatures of weakly-interacting massive particles

An annual modulation in the event rate of the NaI detector of the DAMA collaboration has been used to infer the existence of particle dark matter in the Galactic halo. Bounds on the WIMP mass and WIMP-nucleon cross section have been derived. These analyses have assumed that the local dark-matter velocity distribution is either isotropic or has some bulk rotation. Here we consider the effects of possible structure in the WIMP velocity distribution on the annual-modulation amplitude. We show that if we allow for a locally anisotropic velocity dispersion tensor, the interpretation of direct detection experiments could be altered significantly. We also show that uncertainties in the velocity distribution function that arise from uncertainties in the radial density profile are less important if the velocity dispersion is assumed to be isotropic.
Multiple Gamma Function and Its Application to Computation of Series

The multiple gamma function Γ n , defined by a recurrence-functional equation as a generalization of the Euler gamma function, was originally introduced by Kinkelin, Glaisher, and Barnes around 1900. Today, due to the pioneer work of Conrey, Katz and Sarnak, interest in the multiple gamma function has been revived. This paper discusses some theoretical aspects of the Γ n function and their applications to summation of series and infinite products.
The Role of Holding Company Financial Information in the Insurer‐Rating Process: Evidence From the Property‐Liability Industry

We examine data for the year ended December 31, 1997 for 80 publicly traded property-liability insurers that have Best financial strength ratings of their consolidated insurance-operating subsidiaries. These firms employ a holding company structure, in which a parent owns the stock of multiple insurance-operating subsidiaries. The operating subsidiaries prepare a consolidated annual report using the Statutory Accounting Principles (SAP), and an analogous set of financial statements based on the Generally Accepted Accounting Principles (GAAP) is released by the parent. We find that the financial characteristics important in determining ratings at the individual firm level-capitalization, liquidity, profitability, and size-are also important at the group level. Further, financial ratios from holding company statements are incrementally useful in the ratings' process, after group-level ratios have been taken into account. Robustness tests based on a subsample of holding companies with minimal investment outside of the property-liability industry reinforce our conclusion that parent company statements influence consolidated group ratings. However, our data do not allow us to separate the relative contribution of the GAAP model and underlying transactions to the ratings decision.
A comparison of clustering and missing data methods for health sciences

In this paper, we compare and analyze clustering methods with missing data in health behavior research. In particular, we propose and analyze the use of compressive sensing's matrix completion along with spectral clustering to cluster health related data. The empirical tests and real data results show that these methods can outperform standard methods like LPA and FIML, in terms of lower misclassification rates in clustering and better matrix completion performance in missing data problems. According to our examination, a possible explanation of these improvements is that spectral clustering takes advantage of high data dimension and compressive sensing methods utilize the near-to-low-rank property of health data.
Posters that Foster Cognition in the Classroom: Multimedia Theory Applied to Educational Posters.

Despite a decline in popularity within US society, posters continue to hold a prominent place within middle and high school science classrooms. Teachers’ demand is satisfied by governmental and non-profit science organizations that produce and disseminate posters as tangible products resulting from their research, and instruments to communicate scientific content to teachers and students. In this paper, we examine the design of such posters for their implied, underlying assumptions about learning and their alignment to the unique setting of the classroom. Based on this analysis and research into both cognition and the design of multimedia, we propose a design framework for educational posters that activates students’ attention, catalyzes cognitive processing, provides a framework to guide student’s construction of knowledge and connects to extended learning through live or web-based exploration of phenomenon. Based on this framework, we present a prototype poster and explore implications for poster produc...
Positive selection for unpreferred codon usage in eukaryotic genomes

Natural selection has traditionally been understood as a force responsible for pushing genes to states of higher translational efficiency, whereas lower translational efficiency has been explained by neutral mutation and genetic drift. We looked for evidence of directional selection resulting in increased unpreferred codon usage (and presumably reduced translational efficiency) in three divergent clusters of eukaryotic genomes using a simple optimal-codon-based metric (Kp/Ku). Here we show that for some genes natural selection is indeed responsible for causing accelerated unpreferred codon substitution, and document the scope of this selection. In Cryptococcus and to a lesser extent Drosophila, we find many genes showing a statistically significant signal of selection for unpreferred codon usage in one or more lineages. We did not find evidence for this type of selection in Saccharomyces. The signal of positive selection observed from unpreferred synonymous codon substitutions is coincident in Cryptococcus and Drosophila with the distribution of upstream open reading frames (uORFs), another genic feature known to reduce translational efficiency. Functional enrichment analysis of genes exhibiting low Kp/Ku ratios reveals that genes in regulatory roles are particularly subject to this type of selection. Through genome-wide scans, we find recent selection for unpreferred codon usage at approximately 1% of genetic loci in a Cryptococcus and several genes in Drosophila. Unpreferred codons can impede translation efficiency, and we find that genes with translation-impeding uORFs are enriched for this selection signal. We find that regulatory genes are particularly likely to be subject to selection for unpreferred codon usage. Given that expression noise can propagate through regulatory cascades, and that low translational efficiency can reduce expression noise, this finding supports the hypothesis that translational efficiency may be suppressed in some cases to reduce stochastic noise in gene expression.
Temporal logic programming

Temporal logic, often used as a specification language for programs, can serve directly as a programming language. We propose a specific programming language TEMPLOG, which extends the classical PROLOG-like languages to include temporal operators. PROLOG progams are collections of classical Horn clauses and they are efficiently interpreted by SLD-resolution. Similarly, TEMPLOG programs are collections of temporal Horn clauses and we interpret them with temporal SLD-resolution, a restricted form of a general temporal resolution method.
The system of national accounts for the new economy: What should change?

The publication of the 1993 System of National Accounts served as a major milestone in creating international standards for compiling a fully integrated set of accounts measuring a nation's production, income, and wealth. While statistical agencies continue to make progress toward full implementation of the 1993 SNA, attention is now turning to perceived deficiencies of the system and areas for possible improvement. This paper discusses several suggestions for possible changes in the national accounts, including inclusion of multifactor productivity measures in the production account, changes to the definition of output for certain financial services, expanded coverage of intangible assets, capitalization of military equipment, inclusion of consumer durable goods in measures of saving, imputation of a rate of return to fixed assets used for nonmarket production, reconsideration of sectoral boundaries, and modification of the definition of capital transfers for capital gains taxes.
Periods of orbits for maps on graphs homotopic to a constant map

This paper proves two theorems concerning the set of periods of periodic orbits for maps of graphs that are homotopic to the constant map and such that the vertices form a periodic orbit. The first result is that if the number of vertices is not a divisor of 2 k then there must be a periodic point with period 2 k . The second is that if the number of vertices is for odd s>1, then for all r>s there exists a periodic point of minimum period . These results are then compared to the Sharkovsky ordering of the positive integers.
Economic evaluation of HIV risk reduction intervention in African-American male adolescents.

Purpose: To evaluate the cost-effectiveness of a cognitive-behavioral HIV risk reduction intervention for African-American male adolescents that has previously been shown to be effective at reducing sexual risk taking. Methods: Standard techniques of cost-utility analysis were employed. A societal perspective and a 3% discount rate were used in the main analysis. Program costs were ascertained retrospectively. A mathematical model of HIV transmission was used to translate observed changes in sexual behavior into an estimate of the number of HIV infections the intervention averted. Intervention effects were assumed to last for 1 year. For each infection averted, the corresponding savings in future HIV-related medical care costs and quality-adjusted life years (QALYs) were estimated. The overall net cost per QALY saved (cost-utility ratio) was then calculated. Sensitivity analyses were performed to assess the robustness of the main results. Results: The cost-utility ratio was approximately $57,000 U.S. per QALY saved when training costs were included, and $41,000 U.S. per QALY saved when they were excluded. The intervention appeared substantially more cost-effective when the analysis was restricted to the subgroup of participants who reported being sexually active at baseline. Assumptions about the prevalence of HIV infection and the duration of intervention effectiveness also greatly affected the cost-utility ratio. Conclusions: The HIV prevention intervention was moderately cost-effective in comparison with other health care programs. Selectively implementing the intervention in high-HIV prevalence communities and with sexually active youth can enhance cost-effectiveness.
The spectral density of the QCD Dirac operator and patterns of chiral symmetry breaking

We study the spectrum of the QCD Dirac operator for two colors with fermions in the fundamental representation and for two or more colors with adjoint fermions. For Nf flavors, the chiral flavor symmetry of these theories is spontaneously broken according to SU (2Nf → Sp (2Nf) and SU (Nf → O (Nf), respectively, rather than the symmetry breaking pattern SU (Nf) × SU (Nf) → SU (Nf) for QCD with three or more colors and fundamental fermions. In this paper we study the Dirac spectrum for the first two symmetry breaking patterns. Following previous work for the third case we find the Dirac spectrum in the domain λ ⪡ ΛQCD by means of partially quenched chiral perturbation theory. In particular, this result allows us to calculate the slope of the Dirac spectrum at λ = 0. We also show that for λ ⪡ 1/L2 ΛQCD (wing L the linear size fo the system) the Dirac spectrum is given by a chiral Random Matrix Theory with the symmetries of the Dirac operator.
Sparse choice models

Choice models, which capture popular preferences over objects of interest, play a key role in making decisions whose eventual outcome is impacted by human choice behavior. In most scenarios, the choice model, which can effectively be viewed as a distribution over permutations, must be learned from observed data. The observed data, in turn, may frequently be viewed as (partial, noisy) information about marginals of this distribution over permutations. As such, the search for an appropriate choice model boils down to learning a distribution over permutations that is (near-)consistent with observed information about this distribution. In this work, we pursue a non-parametric approach which seeks to learn a choice model (i.e. a distribution over permutations) with sparsest possible support, and consistent with observed data. We assume that the data observed consists of noisy information pertaining to the marginals of the choice model we seek to learn. We establish that any choice model admits a ‘very’ sparse approximation in the sense that there exists a choice model whose support is small relative to the dimension of the observed data and whose marginals approximately agree with the observed marginal information. We further show that under, what we dub, ‘signature’ conditions, such a sparse approximation can be found in a computationally efficiently fashion relative to a brute force approach. An empirical study using the American Psychological Association election data-set suggests that our approach manages to unearth useful structural properties of the underlying choice model using the sparse approximation found. Our results further suggest that the signature condition is a potential alternative to the recently popularized Restricted Null Space condition for efficient recovery of sparse models.
On the local extension of Killing vector-fields in Ricci flat manifolds

We revisit the extension problem for Killing vector-fields in smooth Ricci flat manifolds, and its relevance to the black hole rigidity problem. We prove both a stronger version of the main local extension result established in [1], as well as two types of results concerning non-extendibility. In particular we show that one can find local, stationary, vacuum extensions of a Kerr solution K(m, a), 0 < a < m, in a future neighborhood of a point p of the past horizon, (p not on the bifurcation sphere), which admits no extension of the Hawking vector-field of K(m, a). This result illustrates one of the major difficulties one faces in trying to extend Hawking’s rigidity result to the more realistic setting of smooth stationary solutions of the Einstein vacuum equations; unlike in the analytic situation, one cannot hope to construct an additional symmetry of stationary solutions (as in Hawking’s Rigidity Theorem) by relying only on local information.
3-D Laser Anemometer Measurements in a Labyrinth Seal

The flow field inside a seven cavity labyrinth seal with a 0.00127 m clearance was measured using a 3-D laser Doppler anemometer system. Through the use of this system, the mean velocity vector and the entire Reynolds stress tensor distributions were measured for the first, third, fifth, and seventh cavities of the seal. There was one large recirculation region present in the cavity for the flow condition tested, Re = 28,000 and Ta = 7,000. The axial and radial mean velocities as well as all of the Reynolds stress term became cavity independent by the third cavity. The azimuthal mean velocity varied from cavity to cavity with its magnitude increasing as the flow progressed downstream.
Generating functions for Hurwitz-Hodge integrals

We describe explicit generating functions for a large class of Hurwitz�Hodge integrals. These are integrals of tautological classes on moduli spaces of admissible covers, a (stackily) smooth compactification of the Hurwitz schemes. Admissible covers and their tautological classes are interesting mathematical objects on their own, but recently they have proved to be a useful tool for the study of the tautological ring of the moduli space of curves, and the orbifold Gromov�Witten theory of DM stacks
Squeeze Play: The Dynamics of the Manipulation End Game

This article considers one of the most significant regulatory concerns facing derivatives markets: the case of market manipulation by means of a corner, or “squeeze.” There are many famous examples of squeezes dating back to the very origins of derivatives trading and extending to the present day. These manipulations distort prices by moving them away from the supply- and demand-driven equilibrium, which limits the effectiveness of the market as a venue for price discovery and effective hedging. Unfortunately, the dynamics of trading as a contract nears expiration have not been modeled extensively. As a result, the existing literature cannot capture many of the interesting actions and interactions observed during actual squeezes. This article fills that void by examining the effects of asymmetrical information on the trading strategies of large longs and shorts as a contract approaches expiration. It provides insight into the mechanism of real-world corners and squeezes and the associated price movements around expiration that are not driven by supply and demand.
Chemical Deposition of TiO2 Layers on GaAs.

Abstract TiO 2 layers were produced on clean etched GaAs by a chemical deposition technique in which a GaAs coupon is immersed in a non-aqueous solution of a titanium alkoxide and then removed to allow the alkoxide layer adhering to the surface to hydrolyze to TiO 2 . Depth profiles of the films were measured by X-ray photoelectron spectroscopy and the scanning Auger microprobe technique, using both ion beam sputter etching and chemical solution etching. The results indicate that the composition and chemical structure of the films are determined by the amount of water present in the coating solution, coating atmosphere and hydrolysis atmosphere. Films grown in high humidity exhibit much intermixing of semiconductor and oxide components, and oxidation of the semiconductor; films grown in low humidity exhibit neither mixing nor oxidation of GaAs unless they are stored in this atmosphere for a prolonged period.
Factoring Euclidean isometries

Every isometry of a finite-dimensional Euclidean space is a product of reflections and the minimum length of a reflection factorization defines a metric on its full isometry group. In this paper we identify the structure of intervals in this metric space by constructing, for each isometry, an explicit combinatorial model encoding all of its minimum length reflection factorizations. The model is largely independent of the isometry chosen in that it only depends on whether or not some point is fixed and the dimension of the space of directions that points are moved.
Adhesion of Shewanella oneidensis MR-1 to Iron (Oxy)(Hydr)Oxides: Microcolony Formation and Isotherm

The adhesion of dissimilatory metal reducing bacteria (DMRB) to iron (oxy)(hydr)oxides may play an important role in their respiration on ferric iron-containing minerals, but few quantitative surfa...
Instrumental background in gamma-ray spectrometers flown in low Earth orbit

Techniques are presented for calculating the instrumental continuum background in gamma-ray spectrometers flown in low earth orbit (LEO), with special attention given to simple methods developed for scaling from the better-understood measurements and calculations of background in balloon-borne instruments to LEO (Gehrels, 1985). Results are presented in the form of predictions of the background and its components for spectrometers in LEO. These predictions are compared to the measured background for the HEAO 3 gamma-ray spectrometer (Mahoney et al., 1980), and predictions are made for the International Gamma-Ray Astrophysics Laboratory mission and the Nuclear Astrophysics Explorer (Matteson et al., 1990) spectrometers. A comparison is made of various orbit options. It is shown that a critical factor is the number of times the instrument passes through the South Atlantic Anomaly (which is the region of enhanced trapped particle fluxes in LEO) and the depth of penetration on each pass.
Preschool vision screening: rationale, methodology and outcome

Although population outcome studies support the utility of preschool screening for reducing the prevalence of amblyopia, fundamental questions remain about how best to do such screening. Infant photoscreening to detect refractive risk factors prior to onset of esotropia and amblyopia seems promising, but our current understanding of the natural history of these conditions is limited, thus limiting the prophylactic potential of early screening. Screening for strabismic, refractive and ocular disease conditions directly associated with amblyopia is more clearly proven, but the diversity of equipment, methods and subject populations studied make it difficult to draw precise summary conclusions at this point about the efficacy of photoscreening. Sensory-based testing of preschool-age children exhibits a similar combination of promise and limitations. The visual acuity tests most widely used for this purpose are prone to problems of testability and false negatives. Moreover, the utility of random-dot stereograms has been confused by misapplication, and new small-target binocularity tests, while attractive, are as yet inadequately field-proven. The evaluation standard for any screening modality is treatment outcome. However, variables in amblyopia classification and quantitative definition differences, timing of presentation, nonequivalent treatment comparisons, and compliance variability have been uncontrolled in virtually all extant studies of amblyopia treatment outcome, making it difficult or impossible to evaluate either the relative efficacy of different treatment regimens for amblyopia or the effects of age on treatment outcome within the preschool age range. The latter issue is a central one, since existence of such an age effect is the primary rationale for screening at younger rather than older preschool ages. The relatively low prevalence of amblyopia makes it difficult to achieve a high screening yield in terms of predictive value, but functionally increasing prevalence by selective screening of high risk populations causes further problems. Unless a "supertest" can be devised, with very high sensitivity and specificity, health policy decisions will be required to determine which of these two characteristics should be emphasized in screening programs. Performance of screening tests can be optimized, however, with adequate training, perhaps via instructional videotapes.
Establishing global policies over decentralized online social networks

Conventional online social networks (OSNs) are implemented in a centralized manner. Although centralization is a convenient way for implementing OSNs, it has several well known drawbacks. Chief among them are the risks they pose to the security and privacy of the information maintained by the OSN; and the loss of control over the information contributed by individual members.
Stereoselective synthesis of concave spacers for long-range electron transfer models

Abstract Syntheses of concave spacers ( 9, 27 ) proceeded via stereoselective Diels-Alder reactions. Successful preparation of asymmetrical spacer 27 relied on regioselective protection of mutual precursor 7 .
Synthesis of Substituted Dihydrobenzofurans via Tandem SNAr/5-Exo-Trig Cyclization

A tandem SNAr/5-exo-trig cyclization reaction is reported that converts N-alkyl- and -arylimines derived from o-fluorobenzaldehydes into 3-amino-2,3-dihydro-2,2-diarylbenzofurans in moderate to good yields. Diarylmethoxide coupling partners serve the dual role of nucleophile in the SNAr step and catalytic base in the cyclization step. With a subset of the substrates, a further base-induced elimination of the 3-amino-2,3-dihydro-2,2-diarylbenzofuran to a phenolic enamine was observed.
Dark Matter Properties and Halo Central Densities

Using an analytic model calibrated against numerical simulations, we calculate the central densities of dark matter halos in a "conventional" cold dark matter model with a cosmological constant (LCDM) and in a "tilted" model (TLCDM) with slightly modified parameters motivated by recent analyses of Lyα forest data. We also calculate how warm dark matter (WDM) would modify these predicted densities by delaying halo formation and imposing phase-space constraints. As a measure of central density, we adopt the quantity ΔV/2, the density within the radius RV/2 at which the halo rotation curve falls to half of its maximum value, in units of the critical density. We compare the theoretical predictions to values of ΔV/2 estimated from the rotation curves of dark matter-dominated disk galaxies. Assuming that dark halos are described by Navarro-Frenk-White profiles, our results suggest that the conventional LCDM model predicts excessively high dark matter densities, unless there is some selection bias in the data toward the low-concentration tail of the halo distribution. A WDM model with particle mass 0.5-1 keV provides a better match to the observational data. However, the modified cold dark matter model, TLCDM, fits the data equally well, suggesting that the solution to the "halo cores" problem might lie in moderate changes to cosmological parameters rather than radical changes to the properties of dark matter. If cold dark matter halos have the steeper density profiles found by Moore et al., then neither conventional LCDM nor TLCDM can reproduce the observed central densities.
The generation of hexamethyl-1,4-disilabenzene and its novel thermal chemistry

Abstract Reaction of a mixture of cis- and trans-1,4-dichlorohexamethyl-1,4-disilacyclohexa-2,5-diene (7) and dilithioanthracenide yields the 9,10-bridged-anthracene adduct of the disilacyclohexadiene, 2. Photolysis or thermolysis of 2 yields transient hexamethyl-1,4-disilabenzene (1), which is trapped by alkynes to give 1,4-disilabarrelenes 8a,8b, by methanol to give 1-methoxy-4-hydrohexamethyl-1,4-disilacyclohexa-2,5-diene (9), and by oxygen to give 1,2,3,4,5,6-hexamethyl-1,4-disila-7-oxa[2.2.1]bicyclohepta-2,5-diene (14). Thermolysis of cis-1,4-dihydrohexamethyl-1,4-disila-cyclohexa-2,5-diene (6) also produces 1, which rearranges at higher temperatures to 2,3,4,5,6-pentamethyl-1,4-disilabicyclo[2.2.1]hepta-2,5-diene (10) and 1,1,3,4-tetramethyl-2,5-dimethylene-1-silacyclopent-3-ene (11). Mechanisms are proposed to account for the observed reactions.
Clans, Cliques, and Captured States : Rethinking “Transition” in Central and Eastern Europe and the Former Soviet Union

Informal systems of relationships may be the most appropriate unit of analysis for understanding the patterns of development of many aspects of corruption, organized crime, markets, and the state. The lack of attention to informal systems can produce unan
Shadows Of Mapping Class Groups: Capturing Convex Cocompactness

We strengthen the analogy between convex cocompact Kleinian groups and convex cocompact subgroups of the mapping class group of a surface in the sense of B. Farb and L. Mosher.
Effects of compressibility on the atomization of liquid jets

the effect of compressibili ty of fluids on the atomization of a liquid jet emanating from a nozzle into the ambient gas is investigated by use of linear stability analysis. An increase in the compressibility of the liquid gas is shown to promote the generation of smaller droplets, although at a slower rate. It is shown that in some parameter ranges, a small change in compressibility may result in a qualitative change of the mechanism of atomization. TOMIZATION is a process of breaking up a liquid jet into droplets of diameter much smaller than the jet di- ameter. This process is widely used in industrial applications including fuel injections in internal combustion engines. A good knowledge of the fundamental mechanism of atomiza- tion is essential for raising the combustion efficiency and re- ducing the environmental pollution. Our understanding of atomization is not yet complete. A concise review of experimental and theoretical work on atomization was given by Reitz and Bracco.1-2 A more ex- tensive exposition of the subject can be found in the work of Lefebvre.3 The atomization process as the consequence of the aerodynamic instability of a jet emanated into ambient gas was investigated by Taylor,4 Levich,5 and others. They con- sidered instability with respect to temporally growing dis- turbances. Atomization as the consequence of convective in- stability caused by spatially growing disturbances was studied by Lin and Kang,6 Lin and Lian,7 and Lin and Creighton.8 In all of the theoretical works mentioned above, the fluids are assumed to be incompressible. On the other hand in many applications, the jet speed is such that the Mach number of the ambient gas relative to the jet may reach transonic. For future applications it may even reach supersonic. Therefore, the compressibility of the fluids must be taken into account. Here, we investigate the effects of compressibility on atom- ization. The problem of instability of an inviscid compressible jet emanating into an inviscid compressible gas is formulated in the next section. The disturbance is allowed to grow both tem- porally and spatially. The results of the solution to the formu- lated problem are used to demonstrate that the compressibility brings about not only quantitative but also qualitative differences in the mechanism of atomization at its onset.
Tachyon condensation in open-closed p-adic string theory

We study a simple model of p-adic closed and open strings. It sheds some light on the dynamics of tachyon condensation for both types of strings. We calculate the effect of static and decaying D-brane configurations on the closed string background. For closed string tachyons we find lumps analogous to D-branes. By studying their fluctuation spectrum and the D-branes they admit, we argue that closed string lumps should be interpreted as spacetimes of lower dimensionality described by some noncritical p-adic string theory.
Minimal surfaces in $$S^3$$ : a survey of recent results

In this survey, we discuss various aspects of the minimal surface equation in the three-sphere $$S^3$$ . After recalling the basic definitions, we describe a family of immersed minimal tori with rotational symmetry. We then review the known examples of embedded minimal surfaces in $$S^3$$ . Besides the equator and the Clifford torus, these include the Lawson and Kapouleas-Yang examples, as well as a new family of examples found recently by Choe and Soret. We next discuss uniqueness theorems for minimal surfaces in $$S^3$$ , such as the work of Almgren on the genus $$0$$ case, and our recent solution of Lawson’s conjecture for embedded minimal surfaces of genus $$1$$ . More generally, we show that any minimal surface of genus $$1$$ which is Alexandrov immersed must be rotationally symmetric. We also discuss Urbano’s estimate for the Morse index of an embedded minimal surface and give an outline of the recent proof of the Willmore conjecture by Marques and Neves. Finally, we describe estimates for the first eigenvalue of the Laplacian on a minimal surface.
New telecommunications technologies require new manners

Abstract This paper considers a number of examples of unmannerly telecommunications behavior. Eight factors differentiating new from traditional forms of telecommunication are identified which are conducive to bad manners. Answering machines, call waiting and speaker phones are considered in greater detail. Fifteen principles are discussed which should inform telecommunications manners for the new technologies. These affirm respect for the dignity of the other person and involve reciprocity, honesty, trust and choice.
Multidimensional quadratic and subquadratic BSDEs with special structure

We study multidimensional BSDEs of the formwith bounded terminal conditions and drivers that grow at most quadratically in . We consider three different cases. In the first case, the BSDE is Markovian, and a solution can be obtained from a solution to a related FBSDE. In the second case, the BSDE becomes a one-dimensional quadratic BSDE when projected to a one-dimensional subspace, and a solution can be derived from a solution of the one-dimensional equation. In the third case, the growth of the driver in is strictly subquadratic, and the existence and uniqueness of a solution can be shown by first solving the BSDE on a short time interval and then extending it recursively.
Redox activity in binucleating Schiff base ligands derived from 1, 4-dihydrazinophthalazine

We report here conclusive evidence that the redox behavior of the dicopper(II) complex is indeed localized on the Schiff base ligand and does not involve oxidation to a dicopper(III) state
Null Cones and Einstein's Equations in Minkowski Spacetime

If Einstein's equations are to describe a field theory of gravity in Minkowski spacetime, then causality requires that the effective curved metric must respect the flat background metric's null cone. The kinematical problem is solved using a generalized eigenvector formalism based on the Segre classification of symmetric rank 2 tensors with respect to a Lorentzian metric. Securing the correct relationship between the two null cones dynamically plausibly is achieved using the naive gauge freedom. New variables tied to the generalized eigenvector formalism reduce the configuration space to the causality-respecting part. In this smaller space, gauge transformations do not form a group, but only a groupoid. The flat metric removes the difficulty of defining equal-time commutation relations in quantum gravity and guarantees global hyperbolicity.
A low variation GHz ring oscillator with addition-based current source

A 3-stage current-starved ring oscillator with 65.1% reduction in process variation in a 90nm CMOS process is presented. The low variation is achieved without degrading the mean operating frequency through the implementation of an addition-based current source to replace a single transistor current source in each inverter stage. No post-fabrication trimming or calibration is required. Circuit simulations indicate that the proposed circuitry is well suited for scaling beyond 90nm. Measurements that are taken from 2 separate wafers and 167 test chips show 65.1% less process variation in output frequency, compared to a conventional current-starved ring oscillator. The power overhead for the additional circuitry is 33µW.
Robust Asymptotic Stability of Desynchronization in Impulse-Coupled Oscillators

The property of desynchronization in an all-to-all network of homogeneous impulse-coupled oscillators is studied. Each impulse-coupled oscillator is modeled as a hybrid system with a single timer state that self-resets to zero when it reaches a threshold, at which event all other impulse-coupled oscillators adjust their timers following a common reset law. In this setting, desynchronization is considered as each impulse-coupled oscillator's timer having equal separation between successive resets. We show that for the considered model, desynchronization is an asymptotically stable property. For this purpose, we recast desynchronization as a set stabilization problem and employ Lyapunov stability tools for hybrid systems. Furthermore, several perturbations are considered showing that desynchronization is a robust property. Perturbations on the continuous and discrete dynamics are considered. Numerical results are presented to illustrate the main contributions.
How do share repurchases affect ownership concentration

Abstract We study how share repurchases affect the ownership stake of outside blockholders in 950 publicly-traded US corporations from 1996 through 2001, using a control function approach to address the possible endogeneity of repurchases. We find that share repurchases tend to make outside ownership less concentrated: repurchasing 1% of outstanding common equity decreases the fraction owned by large shareholders by around one and a half percentage points. This may decrease outside shareholders' influence over firm decision-making. Our results are confirmed when we restrict the sample to institutional owners, but not to individual owners.
Optimization of Lyapunov Invariants in Verification of Software Systems

The paper proposes a control-theoretic framework for verification of numerical software systems, and puts forward software verification as an important application of control and systems theory. The idea is to transfer Lyapunov functions and the associated computational techniques from control systems analysis and convex optimization to verification of various software safety and performance specifications. These include but are not limited to absence of overflow, absence of division-by-zero, termination in finite time, absence of dead-code, and certain user-specified assertions. Central to this framework are Lyapunov invariants. These are properly constructed functions of the program variables, and satisfy certain properties-analogous to those of Lyapunov functions-along the execution trace. The search for the invariants can be formulated as a convex optimization problem. If the associated optimization problem is feasible, the result is a certificate for the specification.
Aspect graphs: An introduction and survey of recent results

The study of the aspect graph of a three-dimensional object has recently become an active area of research in computer vision. The aspect graph provides a complete enumeration of all possible distinct views of an object, given a model for viewpoint space and a definition for “distinct.” This article presents a tutorial introduction to the aspect graph, surveys the current state of the art in algorithms for automatically constructing aspect graphs, and describes some possible applications of aspect graphs in computer vision and computer graphics.
An X-ray monochromator crystal which detects the bragg condition

Abstract We have fabricated a (111) silicon X-ray monochromator crystal with a diode diffused into its surface. Without suffering any apparent degradation in its or rocking-curve width at the Bragg condition, the crystal provides a dc current which changes dramatically at the diffraction of a monochromatic X-ray beam. The current change is directly attributable to extinction at the Bragg angle. It provides a new means to align the two crystals of a double-crystal X-ray monochromator using a feedback circuit.