cssi/SciSciGPT-SciSciNet huggingface dataset:
Scientific Modeling and Simulations

The conceptualization of a problem (modeling) and the computational solution of this problem (simulation),is the foundation of Computational Science. This coupled endeavor is unique in several respects. It allows practically any complex system to be analyzed with predictive capability by invoking the multiscale paradigm linking unit-process models at lower length (or time) scales where fundamental principles have been established to calculations at the system level. The community of multiscale materials modeling has evolved into a multidisciplinary group with a number of identified problem areas of interest. Sidney Yip and Tomas Diaz De La Rubia, the editors of this volume, have gathered 18 contributions that showcase the conceptual advantages of modeling which, coupled with the unprecedented computing power through simulations, allow scientists to tackle the formibable problems of our society, such as the search forhydrocarbons, understanding the structure of a virus, or the intersection between simulations and real data in extreme environments. Scientific Modeling and Simulations advocates the scientific virtues of modeling and simulation, and also encourages the cross fertilization between communities, exploitations of high-performance computing, and experiment-simulation synergies. The contents of this book were previously published in Scientific Modeling and Simulations, Vol 15, No. 1-3, 2008.
Physics education research: the key to student learning

Physics education research differs from traditional education research in that the emphasis is not on educational theory or methodology in the general sense, but rather on student understanding of physics. Such research requires an in-depth knowledge of the subject as well as access to students, which means that it can usually only be carried out by physicists working in physics departments. The findings form a rich resource that provides insights into how students learn physics. When teachers apply this information and document the results for others to use, cumulative improvement in instruction is possible (L C McDermott and E F Redish 1999 Am. J. Phys. 67 755–767).
Jet modification in the next decade: A pedestrian outlook

In this review, we recount the current status of the theory of jet modification in dense matter. We commence with an outline of the ‘traditional’ observables which may be calculated without recourse to event generators. These include single- and double-hadron suppression, nuclear modification factor vs. reaction plane etc. All these measurements are used to justify both the required underlying physical picture of jet modification as well as the final obtained values of jet transport coefficients. This is followed by a review of the more modern observables which have arisen with the ability to reconstruct full jets, and the challenges faced therein. This is followed by a preview of upcoming theoretical developments in the field and an outlook on how the interface between these developments, phenomenological improvements, and upcoming data will allow us to quantitatively determine properties of the medium which effect the modification of hard jets.
REGAL: a regularization based algorithm for reinforcement learning in weakly communicating MDPs

We provide an algorithm that achieves the optimal regret rate in an unknown weakly communicating Markov Decision Process (MDP). The algorithm proceeds in episodes where, in each episode, it picks a policy using regularization based on the span of the optimal bias vector. For an MDP with S states and A actions whose optimal bias vector has span bounded by H, we show a regret bound of O(HS√AT). We also relate the span to various diameter-like quantities associated with the MDP, demonstrating how our results improve on previous regret bounds.
Anytime decision making with imprecise probabilities

This paper examines methods of decision making that are able to accommodate limitations on both the form in which uncertainty pertaining to a decision problem can be realistically represented and the amount of computing time available before a decision must be made. The methods are anytime algorithms in the sense of Boddy and Dean [1989]. Techniques are presented for use with Frisch and Haddawy's [1992] anytime deduction system, with an anytime adaptation of Nilsson's [1986] probabilistic logic, and with a probabilistic database model.
Ectropy-based nonlinear control of FACTS for transient stabilization

This paper concerns a novel approach to the modeling and control design for transient stabilization of electric power systems using Flexible Alternating Current Transmission System (FACTS) devices. A nonlinear dynamic model of general interconnected electric power systems in the Ordinary Differential Equation (ODE) form is proposed in terms of time-varying phasors of all dynamic components. This model captures previously unmodeled fast dynamics of inductors and capacitors of FACTS. Additionally, it allows us to observe the active power which is flowing through FACTS during transients. Using the derived model, an ectropy-based FACTS controller is proposed. The proposed controller regulates the active power through FACTS in order to shift the increment in energy created by disturbances. The energy increment is directed from generators into FACTS, preserving the synchronization between generators during disturbances. Simulation results obtained on the IEEE 14 bus system demonstrate the potential of this controller. The controller is shown to increase critical clearing time of the system in the case of a fault.
Failure of Dst index fields to represent a ring current

[1] Magnetic indices provide valuable information for space weather evaluations. The recent literature shows many scientists still believing that a Dst-derived current circles the Earth like a ring of Saturn. Some actually use a subtraction of Dst to remove the magnetospheric contributions to surface fields. I have measured the storm time fields at paired locations to examine the ring current requirements of surface fields forming the Dst index. Also, I verified the daytime enhancement of the disturbance field at the magnetic dip equator. Two geomagnetic storms were chosen for their size, isolation, seasonal difference, and global data availability. For these storm periods, records from all available stations, within the latitude range of Dst contributors, were collected to choose those pairs of similar longitude. A daytime, dip equator, ionospheric enhancement of the storm fields was verified. Next, the 1/cos (θ) factor, used for the Dst derivation, was applied to the paired data to determine if that ring current adjustment was worthwhile. Results indicate that the local station fields behave more like those from other current sources, such as the ionosphere, and that the cosine factor, representing a magnetospheric ring current effect, typically fails. The Dst appellation “equatorial ring current index” is clearly a misnomer and should be avoided.
Adaptive Test of Conditional Moment Inequalities

Many economic models yield conditional moment inequalities that can be used for inference on parameters of these models. In this paper, I construct new tests of parameter hypotheses in conditional moment inequality models based on studentized kernel estimates of moment functions. The tests automatically adapt to the unknown smoothness of the moment functions, have uniformly correct asymptotic size, and are rate-optimal against certain classes of alternatives. Some existing tests have nontrivial power against n−1/2-local alternatives of a certain type whereas my methods only allow for nontrivial testing against (n / log n)−1/2-local alternatives of this type. There exist, however, large classes of sequences of well-behaved alternatives against which the tests developed in this paper are consistent and those tests are not.
Cosmology, inflation, and the physics of nothing

These four lectures cover four topics in modern cosmology: the cosmological constant, the cosmic microwave background, inflation, and cosmology at the Planck scale. The underlying theme is that cosmology gives us a unique window on the “physics of nothing,” or vacuum energy. The theory of inflation postulates that vacuum energy, or something very much like it, was the dominant force shaping the evolution of the very early universe. Recent astrophysical observations indicate that vacuum energy, or something very much like it, is also the dominant component of the universe today. Therefore cosmology gives us a way to study an important piece of particle physics inaccessible to accelerators. The lectures are oriented toward graduate students with only a passing familiarity with general relativity and knowledge of basic quantum field theory.
Probing neutrino physics with a self-consistent treatment of the weak decoupling, nucleosynthesis, and photon decoupling epochs

We show that a self-consistent and coupled treatment of the weak decoupling, big bang nucleosynthesis, and photon decoupling epochs can be used to provide new insights and constraints on neutrino sector physics from high-precision measurements of light element abundances and Cosmic Microwave Background observables. Implications of beyond-standard-model physics in cosmology, especially within the neutrino sector, are assessed by comparing predictions against five observables: the baryon energy density, helium abundance, deuterium abundance, effective number of neutrinos, and sum of the light neutrino mass eigenstates. We give examples for constraints on dark radiation, neutrino rest mass, lepton numbers, and scenarios for light and heavy sterile neutrinos.
Distributed garbage collection for mobile actor systems: the pseudo root approach

Automatic distributed garbage collection (GC) gives abstraction to grid application development, promoting code quality and improving resource management. Unreachability of active objects or actors from the root set is not a sufficient condition to collect actor garbage, making passive object GC algorithms unsafe when directly used on actor systems. In practical actor languages, all actors have references to the root set since they can interact with users, e.g., through standard input or output streams. Based on this observation, we introduce pseudo roots: a dynamic set of actors that can be viewed as the root set. Pseudo roots use protected (undeletable) references to ensure that no actors are erroneously collected even with messages in transit. Following this idea, we introduce a new direction of actor GC, and demonstrate it by developing a distributed GC framework. The framework can thus be used for automatic life time management of mobile reactive processes with unordered asynchronous communication.
Numerically Invariant Signature Curves

Corrected versions of the numerically invariant expressions for the affine and Euclidean signature of a planar curve introduced by Calabi et al. in (Int. J. Comput. Vision, 26: 107–135, 1998) are presented. The new formulas are valid for fine but otherwise arbitrary partitions of the curve. We also give numerically invariant expressions for the four differential invariants parameterizing the three dimensional version of the Euclidean signature curve, namely the curvature, the torsion and their derivatives with respect to arc length.
Bayesian Budget Feasibility with Posted Pricing

We consider the problem of budget feasible mechanism design proposed by Singer, but in a Bayesian setting. A principal has a public value for hiring a subset of the agents and a budget, while the agents have private costs for being hired. We consider both additive and submodular value functions of the principal. We show that there are simple, practical, ex post budget balanced posted pricing mechanisms that approximate the value obtained by the Bayesian optimal mechanism that is budget balanced only in expectation. A main motivating application for this work is crowdsourcing, e.g., on Mechanical Turk, where workers are drawn from a large population and posted pricing is standard. Our analysis methods relate to contention resolution schemes in submodular optimization of Vondrak et al. and the correlation gap analysis of Yan.
A provable-security treatment of the key-wrap problem

We give a provable-security treatment for the key-wrap problem, providing definitions, constructions, and proofs. We suggest that key-wrap's goal is security in the sense of deterministic authenticated-encryption (DAE), a notion that we put forward. We also provide an alternative notion, a pseudorandom injection (PRI), which we prove to be equivalent. We provide a DAE construction, SIV, analyze its concrete security, develop a blockcipher-based instantiation of it, and suggest that the method makes a desirable alternative to the schemes of the X9.102 draft standard. The construction incorporates a method to turn a PRF that operates on a string into an equally efficient PRF that operates on a vector of strings, a problem of independent interest. Finally, we consider IV-based authenticated-encryption (AE) schemes that are maximally forgiving of repeated IVs, a goal we formalize as misuse-resistant AE. We show that a DAE scheme with a vector-valued header, such as SIV, directly realizes this goal.
Precedence-Constrained Scheduling of Malleable Jobs with Preemption

Scheduling jobs with precedence constraints on a set of identical machines to minimize the total processing time (makespan) is a fundamental problem in combinatorial optimization. In practical settings such as cloud computing, jobs are often malleable, i.e., can be processed on multiple machines simultaneously. The instantaneous processing rate of a job is a non-decreasing function of the number of machines assigned to it (we call it the processing function). Previous research has focused on practically relevant concave processing functions, which obey the law of diminishing utility and generalize the classical (non-malleable) problem. Our main result is a (2 + e)-approximation algorithm for concave processing functions (for any e > 0), which is the best possible under complexity theoretic assumptions. The approximation ratio improves to (1 + e) for the interesting and practically relevant special case of power functions, i.e., p j (z) = c j ·z γ .
A new species of Uncinia (Cyperaceae) from the New World and the first report of U. Chilensis from Argentina

Wheeler, G. A. 2005. A new species of Uncinia (Cyperaceae) from the New World and the first report of U. chilensis from Argentina. Darwiniana 43(1-4): 268-276. A new species of Uncinia (Cyperaceae), U. austroamerica na, is described and illustrated from austral South America and from the Tristan da Cunha archipelago in the south-Atlantic Ocean. This species grows in persistently wet, base-poor sites, particularly in Sphagnum bogs, and is known from southern Patagonia, Tierra del Fuego, and from the largest island of the Tristan da Cunha group. It differs both morphologically and ecologically from the similar-appearing U. macrolepis , a minerotrophic species best known from moist depressions in grasslands. The new species differs morphologically from U. macrolepis by possessing achenes that, when mature, are pale-colored and conspicuously-thickened at the apex and, also, by having more or less loosely-flowered spikes that frequently exceed 2 cm in length. Additionally, U. chilensis is reported for the first time from Argentina.
Online/Offline Attribute-Based Encryption

Attribute-based encryption ABE is a type of public key encryption that allows users to encrypt and decrypt messages based on user attributes. For instance, one can encrypt a message to any user satisfying the boolean formula "crypto conference attendee" AND "PhD student" OR "IACR member". One drawback is that encryption and key generation computational costs scale with the complexity of the access policy or number of attributes. In practice, this makes encryption and user key generation a possible bottleneck for some applications. To address this problem, we develop new techniques for ABE that split the computation for these algorithms into two phases: a preparation phase that does the vast majority of the work to encrypt a message or create a secret key before it knows the message or the attribute list/access control policy that will be used or even the size of the list or policy. A second phase can then rapidly assemble an ABE ciphertext or key when the specifics become known. This concept is sometimes called "online/offline" encryption when only the message is unknown during the preparation phase; we note that the addition of unknown attribute lists and access policies makes ABE significantly more challenging. One motivating application for this technology is mobile devices: the preparation work can be performed while the phone is plugged into a power source, then it can later rapidly perform ABE operations on the move without significantly draining the battery.
Nonlinear bounds in Hölder spaces for the Monge–Ampère equation

Abstract We demonstrate that C 2 , α estimates for the Monge–Ampere equation depend in a highly nonlinear way both on the C α norm of the right-hand side and 1 / α . First, we show that if a solution is strictly convex, then the C 2 , α norm of the solution depends polynomially on the C α norm of the right-hand side. Second, we show that the C 2 , α norm of the solution is controlled by exp ⁡ ( ( C / α ) log ⁡ ( 1 / α ) ) as α → 0 . Finally, we construct a family of solutions in two dimensions to show the sharpness of our results.
Sparse Q-learning with mirror descent

This paper explores a new framework for reinforcement learning based on online convex optimization, in particular mirror descent and related algorithms. Mirror descent can be viewed as an enhanced gradient method, particularly suited to minimization of convex functions in high-dimensional spaces. Unlike traditional gradient methods, mirror descent undertakes gradient updates of weights in both the dual space and primal space, which are linked together using a Legendre transform. Mirror descent can be viewed as a proximal algorithm where the distance generating function used is a Bregman divergence. A new class of proximal-gradient based temporal-difference (TD) methods are presented based on different Bregman divergences, which are more powerful than regular TD learning. Examples of Bregman divergences that are studied include p-norm functions, and Mahalanobis distance based on the covariance of sample gradients. A new family of sparse mirror-descent reinforcement learning methods are proposed, which are able to find sparse fixed points of an l1-regularized Bellman equation at significantly less computational cost than previous methods based on second-order matrix methods. An experimental study of mirror-descent reinforcement learning is presented using discrete and continuous Markov decision processes.
Scarcity, frontiers and development

Resource and land frontiers have always been a significant focus of geography but have become overlooked in economics and economic history. Yet a critical driving force behind global economic development has been the response of human society to natural resource scarcity, not just through conserving scarce resources but also by obtaining and developing more of them. A handful of theories of how such classic frontier expansion has shaped economic development have been formulated, and these are discussed and reviewed. Evidence from history is cited to illustrate these effects, and the implications for resource-based development in the Contemporary Era (1950 to present) are discussed. Unlike previous eras, the pattern of frontier expansion is dualistic. This has led to less economy-wide benefits from frontier-based development in the Contemporary Era.
Discipline in Crisis? The Shifting Paradigm of Mass Communication Research

This article analyzes the Kuhnian paradigmatic status in the field of mass communication. It is suggested that the field's first paradigm, Media Effects, is in a state of crisis rather than a preparadigmatic state or a state of normal science. Finally, this article proposes a description of the current paradigm-in-crisis, suggests ways in which conceptions of the fundamental nature of what we are studying may be shifting, and proposes the elements of a new paradigm which may be emerging in the field.
Oligonucleotide‐Directed Mutagenesis Without Phenotypic Selection

A DNA sequence can be specifically altered by synthesizing the desired sequence change within an oligonucleotide, and then converting this into a biologically active circular DNA strand by using the oligonucleotide to prime in vitro synthesis on a single-stranded circular template. This unit presents a protocol which uses a DNA template containing a small number of uracil residues in place of thymine. Use of the uracil-containing template allows rapid and efficient recovery of mutants; in principle this same template can be applied to most of the other mutagenesis protocols in use. The length of the oligonucleotide primer is highly variable and depends on the nature of the change being made.
AN OBJECTIVE AND PARSIMONIOUS APPROACH FOR CLASSIFYING NATURAL FLOW REGIMES AT A CONTINENTAL SCALE

Hydro-ecological stream classification—the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat—has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to understand similarity in ecological streamflow response. This novel classification approach uses seven fundamental daily streamflow statistics (FDSS) rather than winnowing down an uncorrelated subset from 200 or more ecologically relevant streamflow statistics (ERSS) commonly used in hydro-ecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classification groups derived from the seven FDSS. It is further shown that classification based solely on the 33 ERSS generally does a poorer job in grouping similar streamgauges than the classification based on the seven FDSS. This new classification approach has the additional advantages of overcoming some of the subjectivity associated with the selection of the classification variables and provides a set of robust continental-scale classes of US streamgauges. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
Semidualizing DG modules over tensor products

We study the existence of nontrivial semidualizing DG modules over tensor products of DG algebras over a field. In particular, this gives a lower bound on the number of semidualizing DG modules over the tensor product.
Learning While Voting: Determinants of Collective Experimentation

This paper combines dynamic social choice and strategic experimentation to study the following question: How does a society, a committee, or, more generally, a group of individuals with potentially heterogeneous preferences, experiment with new opportunities ? Each voter recognizes that, during experimentation, other voters also learn about their preferences. As a result, pivotal voters today are biased against experimentation because it reduces their likelihood of remaining pivotal. This phenomenon reduces equilibrium experimentation below the socially efficient level, and may even result in a negative option value of experimentation. However, one can restore efficiency by designing a voting rule that depends deterministically on time. Another main result is that even when payoffs of a reform are independently distributed across the population, good news about any individual's payoff increases other individuals' incentives to experiment with that reform, due to a positive voting externality.
Instabilities and spatio-temporal chaos in hexagon patterns with rotation

Abstract The dynamics of hexagon patterns in rotating systems are investigated within the framework of modified Swift–Hohenberg equations that can be considered as simple models for rotating convection with broken up–down symmetry, e.g. non-Boussinesq Rayleigh–Benard or Marangoni convection. In the weakly nonlinear regime a linear stability analysis of the hexagons reveals long- and short-wave instabilities, which can be steady or oscillatory. The oscillatory short-wave instabilities can lead to stable hexagon patterns that are periodically modulated in space and time, or to a state of spatio-temporal chaos with a Fourier spectrum that precesses on average in time. The chaotic state can exhibit bistability with the steady hexagon pattern. There exist regimes in which the steady hexagon patterns are unstable at all wave numbers.
An explicit height bound for the classical modular polynomial

For a prime l, let Φl be the classical modular polynomial, and let h(Φl) denote its logarithmic height. By specializing a theorem of Cohen, we prove that \(h(\Phi_{l})\le 6l\log l+16l+14\sqrt{l}\log l\). As a corollary, we find that h(Φl)≤6llog l+18l also holds. A table of h(Φl) values is provided for l≤3600.
Price and quality discrimination in durable goods monopoly with resale trading

Abstract We examine a durable goods monopolist’s optimal dynamic price and product quality strategy when buyers are rational and can trade used durables among themselves. In contrast to the usual credibility problem of the durable goods monopolist, intertemporal quality discrimination introduces a time-inconsistency problem of not raising prices against high-valuation consumers who delay purchase for quality upgrades. Resale trading ameliorates this time-inconsistency problem and allows the monopolist to effectively price discriminate, especially when the buyers are patient. The monopolist’s optimal price and quality offers in the new good market exhibit complex dynamic patterns, and new good prices can fall as product quality improves even in the absence of entry threats or learning economies. Initial quality distortions are followed by steady-state quality allocations that are always efficient for the high-valuation buyers, but sometimes also for the marginal consumer-types. Both the resale trading frequency and the price discount for secondhand goods are driven by the pace of strategic quality obsolescence in the new good market.
Characterization of epitaxial films by grazing-incidence X-ray diffraction

Abstract Grazing-incidence X-ray diffraction, a recently developed, powerful, non-destructive and surface-sensitive technique, allows characterization of epitaxial films with thicknesses down to a few atomic layers. Lattice parameters, strains and crystallite sizes can be determined parallel to the interface, complementing results obtained for these parameters in other directions by conventional Bragg diffraction. Epitaxial relationships between substrate and film and their orientational spread can be determined uniquely, and minority domains with an orientation or strain state different from that of the main mass of the film can frequently be detected with this technique while they are not observable with conventional diffraction. The power of this technique, as performed in our laboratory with a 12 kW rotatinganode X-ray generator, is demonstrated with various examples of epitaxial systems: Cu/Al2O3(0001), W/Al2O3 (1 1 02) , molybdenum and niobium on GaAs(001) and GaAs ( 1 1 1 ) , GaAs/Al2O3(0001) and InAs/GaAs(001).
An Efficient General Synthesis of Squarate Esters

Abstract An efficient and general method for the synthesis of alkyl squarates is presented. This involves the reactions of squaric acid with the desired alcohol in the presence of an orthoformate. This was applicable for the synthesis of dimethyl-, diethyl-, diisopropyl, di-n-butyl and di-t-butyl squarates in yields ranging from 77–97%. It is a convenient and safe method that can be accomplished on a multigram scale.
Epoxidation of Olefins by Molecular Oxygen Over Supported Metal Heterogeneous Catalysts

Abstract Molecular oxygen (1 atm) conveniently reacts with olefins in the presence of simple supported metal heterogeneous catalysts and aldehydes (e.g., isobutyraldehyde and benzaldehyde) at room temperature to give epoxides in good yields.
r-Modes on Rapidly Rotating, Relativistic Stars. I. Do Type I Bursts Excite Modes in the Neutron Star Ocean?

During a type I burst, the turbulent deflagration front may excite waves in the neutron star ocean and upper atmosphere with frequencies ω ~ 1 Hz. These waves may be observed as highly coherent flux oscillations during the burst. The frequencies of these waves change as the upper layers of the neutron star cool, which accounts for the small variation in the observed quasi-periodic oscillation (QPO) frequencies. In principle, several modes could be excited, but the fundamental buoyant r-mode exhibits significantly larger variability for a given excitation than all of the other modes. An analysis of modes in the burning layers themselves and the underlying ocean shows that it is unlikely these modes can account for the observed burst oscillations. On the other hand, photospheric modes that reside in a cooler portion of the neutron star atmosphere may provide an excellent explanation for the observed oscillations.
Failure-tolerant parallel programming and its supporting system architecture

The state-of-art in software validation as well as the continuing growth of the size and complexity of software subsystems, makes extra costs paid for software error tolerance more than justified. A program in which software redundancy is incorporated i.e. a program in which procedures for run-time validation and recovery are explicitly specified, is generally called a failure-tolerant program. One problem in failure-tolerant programming, which could be particularly serious in real-time computing environments, is the program execution time increased due to incorporation of validation and recovery procedures. This paper introduces an approach to the solution, called the failure-tolerant parallel programming. The essence of this approach is to maximally overlap main-stream computation with redundant computation oriented for validation and recovery. Subsequently, a model system architecture tailored for efficient execution of failure-tolerant parallel programs is described. It is of highly general and modular nature and contains a novel memory subsystem named the duplex memory. Directions of further researches on program structuring and expansion of the model architecture are also indicated.
Analysis of tradeoff between data accuracy and performance of databases

Databases in large organizations are used for supporting the storage and manipulation of both operational and aggregate data. The operational data is characterized by frequent updates based on changes to values of items in the real world. Aggregate data is used in statistical analysis for decision making, forcasting and formulation of business strategies. The accuracy of the results of statistical processing depends on the processing resources allocated to the update transactions relative to the query and statistical reporting requests. Different types of statistical processing may require varying degress of data accuracy. For example, long range planning decisions may require less accurate data than those needed for tactical decisions. In this paper we propose a model for estimating the accuracy of a database and for the planning of computing resources based on database system performance and accuracy requirements of various groups of users.
[O II] Emission in Quasar Host Galaxies: Evidence for a Suppressed Star Formation Efficiency

The [O II] λ3727 line, a commonly used estimator of star formation rate in extragalactic surveys, should be an equally effective tracer of star formation in the host galaxies of quasars, whose narrow-line regions are expected to produce weak low-ionization emission. Quasar spectra generally show little or no [O II] emission beyond that expected from the active nucleus itself. The inferred star formation rates in optically selected quasars are typically below a few M☉ yr-1, and some are significantly less. Quasars do not appear to occur coevally with starbursts. Recent observations, on the other hand, reveal abundant molecular gas in low-redshift quasars. These two results suggest that the star formation efficiency in quasar host galaxies is somehow suppressed during the active phase of the nucleus. The low star formation rates also imply that the nonstellar nucleus powers the bulk of the thermal infrared emission in radio-quiet quasars.
Is purity eternal

Abstract Phenomenological and formal restrictions on the evolution of pure into mixed states are discussed. In particular, it is argued that, if energy is conserved, loss of purity is incompatible with the weakest possible form of Lorentz covariance.
Real-time computing with lock-free shared objects

This article considers the use of lock-free shared objects within hard real-time systems. As the name suggests, lock-free shared objects are distinguished by the fact that they are accessed without locking. As such, they do not give rise to priority inversions, a key advantage over conventional, lock-based object-sharing approaches. Despite this advantage, it is not immediately apparent that lock-free shared objects can be employed if tasks must adhere to strict timing constraints. In particular, lock-free object implementations permit concurrent operations to interfere with each other, and repeated interferences can cause a given operation to take an arbitrarily long time to complete. The main contribution of this article is to show that such interferences can be bounded by judicious scheduling. This work pertains to periodic, hard real-time tasks that share lock-free objects on a uniprocessor. In the first part of the article, scheduling conditions are derived for such tasks, for both static and dynamic priority schemes. Based on these conditions, it is formally shown that lock-free shared objects often incur less overhead than object implementations based on wait-free algorithms or lock-based schemes. In the last part of the article, this conclusion is validated experimentally through work involving a real-time desktop videoconferencing system.
Tissue-engineered small intestine: ontogeny of the immune system.

Background. Using tissue-engineering techniques, we have developed a neointestine that regenerates structural and transporter properties of native jejunum. The purpose of this study was to characterize the mucosal immune system of the engineered neointestine. We hypothesized that the neointestinal mucosa is capable of developing a mature immunocyte population and that exposure to luminal stimuli is critical to this development. Methods. Neointestinal cysts were engineered by implanting polymer-organoid constructs into syngeneic adult recipients. Neointestine (cysts left nonanastomosed [NA] and cysts anastomosed to native bowel [AN]) and native jejunum were harvested serially (3-56 weeks postoperatively). Immune cell subsets were characterized by the immunohistochemical detection of cell-specific antigens (T cells [CD3], B cells [CD32], NK cells [CD56], and macrophages [CD68]) combined with computer-based morphometry. Results. Intraepithelial and lamina propria immunocyte population densities and subset distributions were identical in AN cysts harvested 20 weeks postoperatively and in native jejunum. Mucosal immunocyte population densities were lower in AN cysts harvested 10 weeks postoperatively and only rudimentary in NA cysts, even those harvested 20 weeks postoperatively. Conclusions. These results suggest that tissue-engineered intestine has the capacity to develop a mucosal immune system with an immunocyte population similar to that of native small intestine. The development of this immune system is a function of both exposure to luminal stimuli and the duration of this exposure. Tissue-engineered intestine offers promise as a new therapeutic approach for patients who have intestinal insufficiency.
Non-blind watermarking of network flows

Linking network flows is an important problem in intrusion detection as well as anonymity. Passive traffic analysis can link flows, but requires long periods of observation to reduce errors. Active traffic analysis, also known as flow watermarking, allows for better precision and is more scalable. Previous flow watermarks introduce significant delays to the traffic flow as a side effect of using a blind detection scheme; this enables attacks that detect and remove the watermark, while at the same time slowing down legitimate traffic. We propose the first non-blind approach for flow watermarking, called RAINBOW, that improves watermark invisibility by inserting delays hundreds of times smaller than previous blind watermarks, hence reduces the watermark interference on network flows. We derive and analyze the optimum detectors for RAINBOW as well as the passive traffic analysis under different traffic models by using hypothesis testing. Comparing the detection performance of RAINBOW and the passive approach, we observe that both RAINBOW and passive traffic analysis perform similarly good in the case of uncorrelated traffic, however the RAINBOW detector drastically outperforms the optimum passive detector in the case of correlated network flows. This justifies the use of non-blind watermarks over passive traffic analysis even though both approaches have similar scalability constraints. We confirm our analysis by simulating the detectors and testing them against large traces of real network flows.
Thermal cycle response of a lead-free solder reinforced with adaptive shape memory alloy

Abstract Shape memory alloy (SMA) discontinuous reinforcements in a solder matrix have the potential to reduce inelastic strains and improve thermo-mechanical fatigue (TMF) life of solder joints. In this work, concept viability was tested on a simpler configuration consisting of a single NiTi wire embedded in a cylindrical Sn–3.5Ag solder matrix. The composite samples were thermally cycled at a constant shear stress under double shear loading perpendicular to the fiber axis, and the local shear displacement was monitored. The local displacement plots indicate significant reduction in creep rate of the SMA reinforced composite versus a control Cu-wire reinforced composite, suggesting that SMA particulate reinforcements may be a feasible option. In order to understand and model the composite response, tests were also conducted on the bare NiTi wire. A preliminary model based on Eshelby's transformation strains provided reasonable agreement with the displacement response of the composites.
The Hyperfine Structure of Hydrogen

The two-body formalism of Schwinger is modified to consider the case of the hydrogen atom. The proton's anomalous moment is treated by adding a Pauli-type term to the Lagrangian. A perturbation theory based upon the Green's function is developed and the first-order correction to the Fermi hyperfine splitting of the ground state is calculated. The method of calculation used is that of Karplus and Klein in their positronium work. Aside from the usual renormalizations encountered, an extra infinity appears in the calculation associated with the assumption of a point anomalous magnetic moment for the proton. On the hypothesis that the proton's moment is actually distributed, cutoffs are inserted. The modified hyperfine formula leads to a new value of $\ensuremath{\alpha}:\frac{1}{\ensuremath{\alpha}}=137.0378$ for a cutoff at the meson length and $\frac{1}{\ensuremath{\alpha}}=137.0374$ for a cutoff at the proton length.
Nuclear Protein Matrix: Association with Newly Synthesized DNA

The residual structural framework of the cell nucleus termed the nuclear protein matrix, is associated with newly synthesized DNA in regenerating rat liver. One minute after rats are injected with [3-H] thymidine, more than 90 percent of the total tritium in nuclear DNA is associated with the matrix DNA although this DNA comprises only 25 percent of the total nuclear DNA. In contrast, the bulk DNA, 75 percent of total nuclear DNA, contains less than 8 percent of the total labeled DNA. The percentage of total labeled DNA associated with the bulk DNA increases for 30 minutes after injection and decreases correspondingly in the matrix DNA.
ZIRCONOCENE-CATALYZED CATIONIC DIELS-ALDER REACTIONS

Abstract In situ prepared Cp2ZrCl⊕ catalyzes the formation of dioxolenium ions from α,β-unsaturated epoxy esters. As a consequence of this activation process, acrylate, methacrylate and crotonate derivatives undergo a rapid and stereoselective cationic [4+2] cycloaddition with a wide range of dienes. Ring-extended carboxylic acid derivatives are formed in 1–7 h at 0–21 °C and in 50–90% yield after saponification of the intermediate diol esters. Simple Lewis acid catalysis by Cp2ZrCl⊕ can be excluded on the basis of the experimental results.
Stability of symmetric spaces of noncompact type under Ricci flow

In this paper we establish stability results for symmetric spaces of noncompact type under Ricci flow, i.e. we show that any small perturbation of the symmetric metric is flown back to the original metric under an appropriately rescaled Ricci flow. It will be important for us which smallness assumptions we have to impose on the initial perturbation. We will find that as long as the symmetric space does not contain any hyperbolic or complex hyperbolic factor, we don’t have to assume any decay on the perturbation. Furthermore, in the hyperbolic and complex hyperbolic case, we show stability under a very weak assumption on the initial perturbation. This will generalize a result obtained by Schulze et al. (Commun Anal Geom 19(5):1023–1047, 2011 ) in the hyperbolic case. The proofs of these results make use of an improved L1-decay estimate for the heat kernel in vector bundles over symmetric spaces, which is of independent interest.
Deducing the Lifetime of Short Gamma-Ray Burst Progenitors from Host Galaxy Demography

The frequency of short gamma-ray bursts (GRBs) in galaxies with distinct star formation histories can be used to constrain the lifetime of the progenitor systems. As an illustration, we consider here the constraints that can be derived from separating the host galaxies into early and late types. On average, early-type galaxies have their stars formed earlier than late-type galaxies, and this difference, together with the time delay between progenitor formation and short GRB outburst, leads to different burst rates in the two types of hosts. Presently available data suggest, but do not yet prove, that the local short GRB rate in early-type galaxies may be comparable to that in late-type galaxies. This suggests that, unlike Type Ia supernovae, at least half of the short GRB progenitors that can outburst within a Hubble time have lifetimes greater than about 7 Gyr. Models of the probability distribution of time delays, here parameterized as P(τ) τn, with n -1 are favored. This apparent long time delay and the fact that early-type galaxies in clusters make a substantial contribution to the local stellar mass inventory can explain the observed preponderance of short GRBs in galaxy clusters.
Getting Real About Abuse and Alienation: A Critique of Drozd and Olesen's Decision Tree

Specialists in abuse and alienation have long taken opposing positions on the legitimacy of the concept of alienation in custody cases where abuse is alleged. One increasingly popular response that appears to carve a middle path is the acknowledgement that both alienation and abuse may co-exist, and a focus on “hybrid” cases, that is, those in which there are cross-allegations of abuse and alienation. This article discusses and critiques, from the perspective of an expert on abuse, one of the earliest and most significant approaches to the hybrid case: Drozd and Olesen's “Decision Tree.” The author concludes that, while the decision tree is a thoughtful and well-intentioned effort to objectively and fairly assess abuse and alienation as well as other potential causes of a damaged child-parent relationship, the “hybrid” approach and some of the Tree's concepts, such as “counter-productive protective parent,” implicitly privilege alienation over abuse, and unintentionally, but inevitably, contribute to the ...
A propagating ATPase gradient drives transport of surface-confined cellular cargo.

The faithful segregation of duplicated genetic material into daughter cells is critical to all organisms. In many bacteria, the segregation of chromosomes involves transport of “centromere-like” loci over the main body of the chromosome, the nucleoid, mediated by a two-protein partition system: a nonspecific DNA-binding ATPase, ParA, and an ATPase stimulator, ParB, which binds to the centromere-like loci. These systems have previously been proposed to function through a filament-based mechanism, analogous to actin- or microtubule-based movement. Here, we reconstituted the F-plasmid partition system using a DNA-carpeted flow cell as an artificial nucleoid surface and magnetic beads coated with plasmid partition complexes as surface-confined cargo. This minimal system recapitulated directed cargo motion driven by a surface ATPase gradient that propagated with the cargo. The dynamics are consistent with a diffusion-ratchet model, whereby the cargo dynamically establishes, and interacts with, a concentration gradient of the ATPase. A chemophoresis force ensues as the cargo perpetually chases the ATPase gradient, allowing the cargo to essentially “surf” the nucleoid on a continuously traveling wave of the ATPase. Demonstration of this non–filament-based motility mechanism in a biological context establishes a distinct class of motor system used for the transport and positioning of large cellular cargo.
Tax‐Based Saving Incentives and Qualified Partial Exclusion Plans

This study examines the effect of two types of qualified partial exclusion (QPE) plans on saving incentives, government revenues, and progressivity. In a “pure” QPE Plan, individual taxpayers who do not deduct any interest expenses on their tax returns can partially exclude their interest, dividend, and capital gain income, subject to a maximum exclusion. In an “expansive” QPE Plan, taxpayers can partially exclude their net investment income (reduced by deductible interest other than home mortgage interest and trade or business interest), subject to a maximum exclusion. The paper considers three alternative exclusion ceilings: $10,000, $15,000, and $20,000 for joint returns and $5,000, $7,500, and $10,000, respectively, for other taxpayers. Depending on the size of the maximum exclusion, the percentage of taxpayers who would be eligible to exclude all of their investment income varies between 77 and 81 percent under a pure QPE Plan and 92 and 96 percent under an expansive QPE Plan.
Efficient parallel algorithms for robot forward dynamics computation

Two efficient parallel algorithms for computing the forward dynamics for real-time simulation were developed for implementation on a single-instruction multiple-data-stream (SIMD) computer with n processors, where n is the number of degrees of freedom of the manipulator. The first parallel algorithm, based on the composite rigid-body method, generates the inertia matrix using the parallel Newton-Euler algorithm, the parallel linear recurrence algorithm, and the modified row-sweep algorithm, and then inverts the inertia matrix to obtain the joint acceleration vector at time t. The time complexity of this parallel algorithm is of the order O(n/sup 2/) with O(n) processors. The second parallel algorithm, based on the conjugate gradient method, computes the joint acceleration with a time complexity of O(n) for multiplication operation and O(n log/sub 2/n) for addition operation. The interprocessor communication problem for the implementation of the proposed parallel algorithms on SIMD machines is also discussed and analyzed. >