cssi/SciSciGPT-SciSciNet huggingface dataset:
Chemoselective modification of proteins: hitting the target

The use of synthetic molecules to modulate and track biological events is a central component of chemical biology. As a result, the precise, covalent modification of biomolecules is a key goal for this field. Several strategies have emerged that allow specific tailoring of polypeptides through either endogenous residues or introduced functionality. This tutorial review discusses these recent advances in the context of in vitro and in vivo applications.
Improved approximation algorithms for the single-sink buy-at-bulk network design problems

Consider a given undirected graph G=(V,E) with non-negative edge lengths, a root node r@?V, and a set D@?V of demands with d"v representing the units of flow that demand v@?D wishes to send to the root. We are also given K types of cables, each with a specified capacity and cost per unit length. The single-sink buy-at-bulk (SSBB) problem asks for a low-cost installation of cables along the edges of G, such that the demands can simultaneously send their flow to root r. The problem is studied with and without the restriction that the flow from a node must follow a single path to the root. We are allowed to install zero or more copies of a cable type on each edge. The SSBB problem is NP-hard. In this paper, we present a 153.6-approximation algorithm for the SSBB problem improving the previous best ratio of 216. For the case in which the flow is splittable, we improve the previous best ratio of 76.8 to @a"K, where @a"K is less than 67.94 for all K. In particular, @a"2<17.7, @a"3<23.2, @a"4<28.8, and @a"5<34.3.
Orbifold singularities, Lie algebras of the third kind (LATKes), and pure Yang-Mills with matter

We discover the unique, simple Lie algebra of the third kind, or LATKe, that stems from codimension 6 orbifold singularities and gives rise to a new kind of Yang–Mills theory which simultaneously is pure and contains matter. The root space of the LATKe is one-dimensional and its Dynkin diagram consists of one point. The uniqueness of the LATKe is a vacuum selection mechanism. TheWorldinaPoint?Blow-upofC3/Z3|DynkindiagramoftheLATKe●PureYang-Millswithmatter
Mild Methodology for [4+1] Pyrroline Annulation. Second Generation Synthesis of Pyrrolizidine Alkaloids

Abstract Vinylaziridine 2 underwent alkylative ring opening with trimethylsilyl iodide to furnish supinidine ethyl ester 4 from which supinidine 5, isoretronecanol 7, and trachelanthamidine 9 were synthesized stereoselectively.
Episodic priming in children with learning disabilities

Abstract Previous research has consistently demonstrated that children with learning disabilities experience greater difficulty than nondisabled children in their attempts to learn new associations (e.g., Lorsbach & Worman, 1988) . The present experiment used a traditional cued recall task, as well as an item recognition priming paradigm (Ratcliff & McKoon, 1978) , to obtain information about the locus of associative memory difficulties in learning disabled children. Consistent with earlier studies, learning disabled children were found to experience greater difficulty than nondisabled children when tested with a cued recall task. In contrast, the results of the item recognition priming task indicated that recently studied associations produced equal amounts of priming in learning disabled and nondisabled children. On the basis of the results of these two measures of associative memory, it was argued that learning disabled children had formed recently studied associations, despite their inability to consciously bring them back to mind on an episodic memory task. Results were discussed within the explicit and implicit memory framework of Graf and Schacter (1985) .
Infrared effects and the asymptotics of perturbation theory in weak decays of heavy particles

I discuss the interplay of infrared sensitivity in large order perturbative expansions with the presence of explicit nonperturbative corrections in the context of heavy quark expansions. The main focus is on inclusive decays and the status of the kinetic energy of the heavy quark. This talk summarizes work done with Braun and Zakharov.
Ligand-Controlled Asymmetric Arylation of Aliphatic α-Amino Anion Equivalents

A palladium-catalyzed asymmetric arylation of 9-aminofluorene-derived imines using a chiral dialkylbiaryl phosphine as the supporting ligand has been developed. This transformation allows for enantioselective access to a diverse range of α-branched benzylamines.
AN EVOLUTIONARY EXPLANATION FOR ROTTEN KIDS

We explore how natural selection acts upon genes for cooperation, altruism and selfishness in an prisoner's dilemma played by family members. A key parameter determining behavior is that parents and children have different expectations of future offspring. Examining asexual and sexually reproducing populations we show that which strategy of cooperation and defection proves be stable depends on the relative reproduction potential of the players and what proportion of the population is young. “Rotten kids” with altruistic parents can be a stable outcome where reproductive success is the goal, and natural selection may lead individuals to care about their unborn progeny. (JEL D10, H31)
Constructing and sampling graphs with a prescribed joint degree distribution

One of the most influential recent results in network analysis is that many natural networks exhibit a power-law or log-normal degree distribution. This has inspired numerous generative models that match this property. However, more recent work has shown that while these generative models do have the right degree distribution, they are not good models for real-life networks due to their differences on other important metrics like conductance. We believe this is, in part, because many of these real-world networks have very different joint degree distributions, that is, the probability that a randomly selected edge will be between nodes of degree k and l. Assortativity is a sufficient statistic of the joint degree distribution, and it has been previously noted that social networks tend to be assortative, while biological and technological networks tend to be disassortative.We suggest understanding the relationship between network structure and the joint degree distribution of graphs is an interesting avenue of further research. An important tool for such studies are algorithms that can generate random instances of graphs with the same joint degree distribution. This is the main topic of this article, and we study the problem from both a theoretical and practical perspective. We provide an algorithm for constructing simple graphs from a given joint degree distribution, and a Monte Carlo Markov chain method for sampling them. We also show that the state space of simple graphs with a fixed degree distribution is connected via endpoint switches. We empirically evaluate the mixing time of this Markov chain by using experiments based on the autocorrelation of each edge. These experiments show that our Markov chain mixes quickly on these real graphs, allowing for utilization of our techniques in practice.
Representations of surface groups and right-angled Artin groups in higher rank

We give concrete constructions of discrete and faithful representations of right-angled Artin groups into higher-rank Lie groups. Using the geometry of the associated symmetric spaces and the combinatorics of the groups, we find a general criterion for when discrete and faithful representations exist, and show that the criterion is satisfied in particular cases. There are direct applications towards constructing representations of surface groups into higher-rank Lie groups, and, in particular, into lattices in higher-rank Lie groups. 20F36; 53C35
Light trapping and enhancing gold nanoparticle array substrates made by thermal dewetting technique

In this paper, we fabricated gold particle array substrate by thermal dewetting technique. The fabrication process is simple, reliable, cost efficient with comparing to other techniques. From optical characteristic it shows light trapping ability to reduce reflectance around 75%. Combining light trapping and its localized plasmonic properties, this substrate has significant advantages on plasmonic based sensing methods such as surface enhanced Raman scattering (SERS). SERS measurement has been performed and the enhancement factor is 2.58×10 5 . Further more, after silver thin film deposition the enhancement can be increased up to 2 orders and the enhancement factor is 3.66×10 7 .
The Mass of the Convective Zone in FGK Main-Sequence Stars and the Effect of Accreted Planetary Material on Apparent Metallicity Determinations

The mass of the outer convective zone in FGK main-sequence stars decreases dramatically with stellar mass. Therefore, any contamination of a star's atmosphere by accreted planetary material should affect hotter stars much more than cool stars. If high metal abundances in stars with planets were from planetesimal accretion, then metallicity enhancements in earlier type stars with planets should be very pronounced. No such trend is seen, however.
Turbulence-Generated Pressure Fluctuations in a Rocket-Like Cavity

Theoretical acoustics applied to the pipe flow turbulence problem in a configuration that was experimentally investigated yields an analytical formula for random pressure fluctuations generated by the turbulence. In order to calculate the pressure fluctuations, it is found that certain spatial correlations of the fluctuation in the square of the axial velocity are needed. These are measured by hot-film anemometry, as are the pressure fluctuations, in a fully developed pipe flow and the theory is shown to be semiquantitative; a lower bound to the pressure fluctuation emerges. Application to the problem of pressure fluctuations in rocket motors and attendant vibration are indicated. ITU Nomenclature A = pipe cross-sectional area A cor = correlation area of turbulence a = pipe radius c — speed of sound / = quantity defined by Eq. (6) gu = Green's function for plane wave acoustics problem g = Green' s function for H H = Bernoulli enthalpy Jm = Bessel function of order m t. = duct length £cor = axial correlation length scale of turbulence n = outward unit normal vector p = pressure Sfj. = cross-spectral density between signal / and signal j SIf = cross spectrum of pressure due to local turbulence = cross spectrum of pressure due to propagational sound smn = eigenvalue in the problem for H
Shear wave velocity measurements using acoustic radiation force impulse in young children with normal kidneys versus hydronephrotic kidneys.

Purpose: To measure shear wave velocities (SWVs) by acoustic radiation force impulse (ARFI) ultrasound elastography in normal kidneys and in hydronephrotic kidneys in young children and to compare SWVs between the hydronephrosis grades.
Ion beam processes in Si

Abstract Observation of the effects of implants of energetic ions at high dose rates into-Si have produced some exciting and interesting results. The mechanism whereby displacement damage produced by ions self-anneals during high dose rate implantation will be discussed. It will be shown that ion beam annealing (IBA) offers in certain situations unique possibilities for damage annealing. Annealing results of the near surface in Si with a buried oxide layer, formed by high dose implantation, will be presented in order to illustrate the advantages offered by IBA. It will be also shown that ion irradiation can stimulate the epitaxial recrystallization of amorphous overlayers in Si. The nonequilibrium alloying which results from such epitaxial processes will be discussed as well as mechanisms which limit the solid solubility during irradiation. Finally, a dose rate dependency for the production of stable damage by ion irradiation at a constant fluence has been observed. For low fluence implants, the amount of damage is substantially greater in the case of high flux rather than low flux implantation.
A convenient preparation of 1,2-diacylglycerols; o-iodobenzoyl as a protecting group

Abstract The o -iodobenzoyl moiety is a useful 3-hydroxyl protecting group in the synthesis of 1,2-diacylglycerols; it can be removed by chlorination followed by mild basic hydrolysis.
Methylation of aromatics with Me3S+, Me3Se+, and Me3Te+ in superacid media

Abstract Electrophilic reactivity of Me3S+ O Tf, Me3Se+ O Tf, and Me3Te+ O Tf ( O Tf= trifluoromethanesulfonate) in superacid solvents towards aromatics has been dem-onstrated, indicative of protosolvation of the remaining lone pair on the onium ions. When dissolved in superacids, Me3Se+ O Tf and Me3Te+ O Tf show measurable changes in their NMR (1H, 13C, 77Se, 125Te) chemical shifts and one bond 77Se-13C,125Te-13C spin-spin coupling constants. The NMR data are compared with those of related selenonium cations and donor-acceptor complexes.
On rack cohomology

Abstract We prove that the lower bounds for Betti numbers of the rack, quandle and degeneracy cohomology given in Carter et al. (J. Pure Appl. Algebra, 157 (2001) 135) are in fact equalities. We compute as well the Betti numbers of the twisted cohomology introduced in Carter et al. (Twisted quandle cohomology theory and cocycle knot invariants, math. GT/0108051). We also give a group-theoretical interpretation of the second cohomology group for racks.
Parallelism in logic programs

There is a tension between the objectives of avoiding irrelevant computation and extracting parallelism, in that a computational step used to restrict another must precede the latter. Our thesis, following [3], is that evaluation methods can be viewed as implementing a choice ofsideways information propagation graphs, or sips, which determines the set of goals and facts that must be evaluated. Two evaluation methods that implement the same sips can then be compared to see which obtains a greater degree of parallelism, and we provide a formal measure of parallelism to make this comparison. Using this measure, we prove that transforming a program using the Magic Templates algorithm and then evaluating the fixpoint bottom-up provides a “most parallel” implementation for a given choice of sips, without taking resource constraints into account. This result, taken in conjunction with earlier results from [3,27], which show that bottom-up evaluation performs no irrelevant computation and is sound and complete, suggests that a bottom-up approach to parallel evaluation of logic programs is very promising. A more careful analysis of the relative overheads in the top-down and bottom-up evaluation paradigms is needed, however, and we discuss some of the issues. The abstract model allows us to establish several results comparing other proposed parallel evaluation methods in the logic programming and deductive database literature, thereby showing some natural, and sometimes surprising, connections. We consider the limitations of the abstract model and of the proposed bottom-up evaluation method, including the inability of sips to describe certain evaluation methods, and the effect of resource constraints. Our results shed light on the limits of the sip paradigm of computation, which we extend in the process.
Modules, Comodules, and Cotensor Products over Frobenius Algebras

Abstract We characterize noncommutative Frobenius algebras A in terms of the existence of a coproduct which is a map of left Ae-modules. We show that the category of right (left) comodules over A, relative to this coproduct, is isomorphic to the category of right (left) modules. This isomorphism enables a reformulation of the cotensor product of Eilenberg and Moore as a functor of modules rather than comodules. We prove that the cotensor product M□N of a right A-module M and a left A-module N is isomorphic to the vector space of homomorphisms from a particular left Ae-module D to N ⊗ M, viewed as a left Ae-module. Some properties of D are described. Finally, we show that when A is a symmetric algebra, the cotensor product M□N and its derived functors are given by the Hochschild cohomology over A of N ⊗ M.
Asymptotically good codes correcting insertions, deletions, and transpositions

We present simple, polynomial time encodable and decodable codes which are asymptotically good for channels allowing insertions, deletions, and transpositions. As a corollary, they achieve exponential error probability in a stochastic model of insertion-deletion.
Vitrification of high-level wastes: A review of the computer thermal analyses for storage canisters

Abstract CANIST, a two-dimensional (r and θ) computer program that solves the unsteady-state, heat-conduction equation, was used to model the thermal behavior of canisters filled with waste glass. CANIST has been found to be a valuable analytical tool for predicting the temperature profile of a waste storage canister as a function of several variables, including the diameter of the canister, the placement of internal fins, the heat generation rate of the waste glass, and the thermophysical properties of the canister and the waste glass. Thus, temperature-dependent processes that may affect the integrity of the glass/canister unit, for example cracking, can be investigated using an analytical approach.
A Genetic Algorithm Optimization Technique for Compact High Intensity Cooler Design

This paper initially reviews the operation and design criteria for a compact high intensity cooler (CHIC) unit as used in avionic equipment. Here high heat loads are dissipated via multiple impinging jets fed sequentially through a series of fins connected with a bus bar to the heat source. The analytical basis for the heat transfer design, most of which has been published previously, is shown to predict the performance of CHIC units to a high degree of accuracy. This then permits an approach at optimizing the design. Most optimization techniques depend on continuous variables, while in the design of a CHIC unit many of the critical geometrical variables must assume discrete values. A genetic algorithm, generally not well known in engineering circles, that looks for an optimum by simulating an evolutionary process was found to be satisfactory for this problem with its mixture of discrete and continuous variables. It is also shown that in an actual optimization problem, where the fluid pressure drop across the unit has to be balanced against a low overall thermal resistance, an optimum geometrical design can be determined. This design is an improvement over the empirical best design previously reported the literature.
On optimality of stepdown and stepup multiple test procedures

Consider the multiple testing problem of testing k null hypotheses, where the unknown family of distributions is assumed to satisfy a certain monotonicity assumption. Attention is restricted to procedures that control the familywise error rate in the strong sense and which satisfy a monotonicity condition. Under these assumptions, we prove certain maximin optimality results for some well-known stepdown and stepup procedures.
A Note on the Selection of Time Series Models

We consider issues related to the order of an autoregression selected using information criteria. We study the sensitivity of the estimated order to (i) whether the effective number of observations is held fixed when estimating models of different order, (ii) whether the estimate of the variance is adjusted for degrees of freedom, and (iii) how the penalty for overfitting is defined in relation to the total sample size. Simulations show that the lag length selected by both the Akaike and the Schwarz information criteria are sensitive to these parameters in finite samples. The methods that give the most precise estimates are those that hold the effective sample size fixed across models to be compared. Theoretical considerations reveal that this is indeed necessary for valid model comparisons. Guides to robust model selection are provided.
Large chiral discrimination of a molecular probe by bovine serum albumin

A phenylalanine-derived fluorescent probe shows high enantioselectivity for binding to bovine serum albumin; the L-isomer binds nearly one hundred times better than the D-isomer, which suggests the tight fitting of the L-isomer to the binding site.
Galton, Edgeworth, Frisch, and prospects for quantile regression in econometrics

The work of three leading figures in the early history of econometrics is used to motivate some recent developments in the theory and application of quantile regression. We stress not only the robustness advantages of this form of semiparametric statistical method, but also the opportunity to recover a more complete description of the statistical relationship between variables. A recent proposal for a more X-robust form of quantile regression based on maximal depth ideas is described along with an interesting historical antecedent. Finally, the notorious computational burden of median regression, and quantile regression more generally, is addressed. It is argued that recent developments in interior point methods for linear programming together with some new preprocessing ideas make it possible to compute quantile regressions as quickly as least-squares regressions throughout the entire range of problem sizes encountered in econometrics.
Nonlocal radial dependence of laser-induced molecular reorientation in a nematic liquid crystal: theory and experiment

We present a detailed theoretical calculation, with experimental verification, of the nonlocal molecular reorientation of the nematic-liquid-crystal director axis induced by a cw Gaussian laser beam. The natures of the torque balance equations and the solutions are significantly different for normally and nonnormally incident laser beams. The nonlocal effects resulting from molecular correlation effects are particularly important for laser spot sizes that are different (smaller or larger) from the sample thickness. Experimental measurements for the transverse dependence of the molecules and the dependence of the Freedericksz threshold as a function of the laser beam sizes are in excellent agreement with theoretical results. We also comment on the effect of these nonlocal effects on transverse optical bistability.
Assessing the Process Maturity Utilized in Software Engineering Team Project Courses

Many computer science departments offer an introductory software engineering course, which normally provides an introduction to software engineering topics in conjunction with a semester long team project. To ensure students acquire the correct lessons from this project experience, it is essential that the teams utilize well-defined software development processes similar to those practiced by leading software development organizations. Since its inception, the Software Engineering Institute Capability Maturity Model (CMM) has served as a guide for organizations seeking to improve their development practices, through a self-assessment questionnaire. In an effort to assess the maturity of development practices utilized in software engineering courses, an “academic” version of the CMM questionnaire was developed. This questionnaire was distributed to a sample of software engineering instructors in an effort to assess the maturity of academic software engineering course projects. The questionnaire and the survey results are presented and discussed.
Dynamics of k-core percolation

In many network applications nodes are stable provided they have at least k neighbours, and a network of k-stable nodes is called a k-core. The vulnerability to random attack is characterized by the size of culling avalanches which occur after a randomly chosen k-core node is removed. Simulations of lattices in two, three and four dimensions, as well as small-world networks, indicate that power-law avalanches occur in first-order k-core systems, while truncated avalanches are characteristic of second-order cases.
Chemical modification of catalyst support for enhancement of transient catalytic activity: nitric oxide reduction by carbon monoxide over rhodium

A commercial ceria powder was chemically modified by doping with gadolinia in order to improve its oxygen storage/transport characteristics. The catalytic activity of Rh impregnated on this modified ceria support was measured and compared with those impregnated on conventional ceria or alumina support, using a packed-bed reactor and an isotopic reactant (13CO) for the NO + CO reaction under both cycled- and steady-feed conditions. Results of transient pulse experiments indicated that the oxygen uptakes of both ceria and modified ceria are an order of magnitude greater than that of alumina. This work has demonstrated that the chemical modification of the ceria support can significantly enhance the catalytic activity of Rh for the NO + CO reaction under cycled feedstream conditions at high temperatures above 500°C. This enhancement of catalytic activity of Rh supported on the modified ceria is discussed in light of the oxygen storage and transport characteristics of the modified support.
A continuous approximation procedure for determining inventory distribution schemas within supply chains

This paper presents an integrated inventory distribution optimization model that simultaneously incorporates the issues of location, production, inventory, and transportation within a supply chain. The objective is to determine the optimal number and size of shipments under varying but commonly practiced production and shipping scenarios. A continuous approximation procedure is proposed to determine the optimal number and size of shipments. Three production and shipping scenarios are investigated and closed form expressions for the optimal number of shipments for each scenario are obtained. A numerical example is presented to demonstrate the usefulness of the model.
Truncated predictor feedback control for exponentially unstable linear systems with time-varying input delay☆

Abstract The stabilization of exponentially unstable linear systems with time-varying input delay is considered in this paper. We extend the truncated predictor feedback (TPF) design method, which was recently developed for systems with all poles on the closed left-half plane, to be applicable to exponentially unstable linear systems. Assuming that the time-varying delay is known and bounded, the design approach of a time-varying state feedback controller is developed based on the solution of a parametric Lyapunov equation. An explicit condition is derived for which the stability of the closed-loop system with the proposed controller is guaranteed. It is shown that, for the stability of the closed-loop system, the maximum allowable time-delay in the input is inversely proportional to the sum of the unstable poles in the plant. The effectiveness of the proposed method is demonstrated through numerical examples.
Thermal Analysis of Some Flat-Plate Solar Collector Designs for Improving Performance

The effects of suppression of thermal radiation, conduction and/or free convection heat loss from the absorber of a flat-plate solar collector are analytically studied. A two-dimensional, steady-state, heat-transfer analysis is developed for a collector for this purpose. The analysis accounts for the temperature gradients in the fluid flow and vertical directions in the collector, the collimated and diffuse nature of solar irradiation, the physical and thermodynamic properties of the materials in the collector, the number of cover plates, any selective surfaces, and the collector dimensions. The spectral nature of radiation heat transfer in the collector is modeled by two spectral bands, solar and thermal. The results illustrate that a single selective surface on the absorber or on the cover plate closest to the absorber to suppress thermal radiation heat loss is the most effective means of improving flat-plate collector performance when only suppressing one mode of heat transfer. Honeycomb structures placed in the air gap between the absorber and cover plate to suppress free convection or evacuation of the air gap to eliminate conduction and free convection are not as effective a method of improving collector performance as selective surfaces at higher (> 100°C) collector temperatures.
Reconsidering the Relationship between Inflation and Relative Price Variability

It has long been popularly believed that the relationship between inflation and relative price variability (RPV) is positive and stable. Using disaggregated CPI data for the United States and Japan, however, this study finds that the relationship is neither linear nor stable over time. The overall relationship is approximately U-shaped around a nonzero threshold inflation rate. RPV therefore changes not with the inflation rate per se, but with the deviation of inflation from the threshold inflation rate. More importantly, the relationship is by no means stable over time but instead varies significantly in a way that coincides with regime changes of inflation or monetary policy. The relationship was positive during the period of high inflation of the 1970s and the early 1980s, as has been documented by a number of previous studies, whereas it takes a U-shape profile during the Great Moderation. The results are robust to the use of core inflation, which excludes the traditionally volatile prices of food and energy. This paper then presents a modified version of the Calvo-type sticky price model to describe the observed empirical regularities. Simulation experiments show that the modified Calvo model fits the data well, and that the underlying relationship hinges upon the degree of price rigidity, which is systematically related to inflation regime. For countries and periods with low inflation rates, the relationship takes a U-shape as price adjustment is more sticky. In a high-inflation environment, when price setting becomes more flexible, the U-shaped profile vanishes.
Evidence of charge exchange pumping in calcium−xenon system

A flowing xenon plasma seeded with calcium was used to investigate the population mechanism for the 5s and 4d levels of Ca+. From the dependence of certain line intensity ratios on electron temperature it was concluded that charge exchange between Xe+ and Ca is the predominate mechanism for populating the 5s and 4d levels. Comparison with intensity ratios obtained in Ca−Ar and Ca−Kr imply the same conclusion.
Electronic Properties of Graphite Intercalation Compounds

The highly anisotropic bonding in graphite facilitates the intercalation of a wide variety of chemical species between the hexagonal carbon monolayers [1]. One is immediately led to consider differences and similarities between graphite intercalation compounds (GIC’s) and the intercalation complexes of the transition metal dichalcogenides (TMD’s). The graphite system provides much greater variety at the synthetic level, through manipulation of the two independent variables specie and ‘stage’. Some 60-odd intercalant species are known, including alkali metals, alkaline earths, rare earths, halogens, protonic and Lewis acids. Co-intercalation with two species, one of which may be an organic molecule, is also quite common. In contrast to intercalated TMD’s one can usually obtain a series of stoichiometric GIC’s with a given specie, corresponding to an integral number n of carbon layers separating nearest intercalant monolayers. The integer n is called the stage of the compound, stage 1 usually being the saturation concentration. Assuming that on average stages 1 through 4 can be reliably synthesized, the family of GIC’s comprises at least 240 distinct compounds, and this number continues to grow.
String Cosmology and the Dimension of Spacetime

The implications of string theory for understanding the dimension of uncompactified spacetime are investigated. Using recent ideas in string cosmology, a new model is proposed to explain why three spatial dimensions grew large. Unlike the original work of Brandenberger and Vafa, this paradigm uses the theory of random walks. A computer model is developed to test the implications of this new approach. It is found that a four-dimensional spacetime can be explained by the proper choice of initial conditions.
The limit distribution of the estimates in cointegrated regression models with multiple structural changes

Abstract We study estimation and inference in cointegrated regression models with multiple structural changes allowing both stationary and integrated regressors. Both pure and partial structural change models are analyzed. We derive the consistency, rate of convergence and the limit distribution of the estimated break fractions. Our technical conditions are considerably less restrictive than those in Bai et al. [Bai, J., Lumsdaine, R.L., Stock, J.H., 1998. Testing for and dating breaks in multivariate time series. Review of Economic Studies 65, 395–432] who considered the single break case in a multi-equations system, and permit a wide class of practically relevant models. Our analysis is, however, restricted to a single equation framework. We show that if the coefficients of the integrated regressors are allowed to change, the estimated break fractions are asymptotically dependent so that confidence intervals need to be constructed jointly. If, however, only the intercept and/or the coefficients of the stationary regressors are allowed to change, the estimates of the break dates are asymptotically independent as in the stationary case analyzed by Bai and Perron [Bai, J., Perron, P., 1998. Estimating and testing linear models with multiple structural changes. Econometrica 66, 47–78]. We also show that our results remain valid, under very weak conditions, when the potential endogeneity of the non-stationary regressors is accounted for via an increasing sequence of leads and lags of their first-differences as additional regressors. Simulation evidence is presented to assess the adequacy of the asymptotic approximations in finite samples.
Integrated assessment of abrupt climatic changes

One of the most controversial conclusions to emerge from many of the first generation of integrated assessment models (IAMs) of climate policy was the perceived economic optimality of negligible near-term abatement of greenhouse gases. Typically, such studies were conducted using smoothly varying climate change scenarios or impact responses. Abrupt changes observed in the climatic record and documented in current models could substantially alter the stringency of economically optimal IAM policies. Such abrupt climatic changes — or consequent impacts — would be less foreseeable and provide less time to adapt, and thus would have far greater economic or environmental impacts than gradual warming. We extend conventional, smooth IAM analysis by coupling a climate model capable of one type of abrupt change to a well-established energy–economy model (DICE). We compare the DICE optimal policy using the standard climate sub-model to our version that allows for abrupt change — and consequent enhanced climate damage — through changes in the strength (and possible collapse) of the North Atlantic thermohaline circulation (THC). We confirm the potential significance of abrupt climate change to economically optimal IAM policies, thus calling into question all previous work neglecting such possibilities — at the least for the wide ranges of relevant social and climate system parameters we consider. In addition, we obtain an emergent property of our coupled social–natural system model: “optimal policies” that do consider abrupt changes may, under relatively low discount rates, calculate emission control levels sufficient to avoid significant abrupt change, whereas “optimal policies” disregarding abrupt change would not prevent this non-linear event. However, there is a threshold in discount rate above which the present value of future damages is so low that even very large enhanced damages in the 22nd century, when a significant abrupt change such as a THC collapse would be most likely to occur, do not increase optimal control levels sufficiently to prevent such a collapse. Thus, any models not accounting for potential abrupt non-linear behavior and its interaction with the discounting formulation are likely to miss an important set of possibilities relevant to the climate policy debate. © 2001 Elsevier Science B.V. All rights reserved.
THE LIMIT OF MAGNETIC-SHEAR ENERGY IN SOLAR ACTIVE REGIONS

It has been found previously, by measuring from active-region magnetograms a proxy of the free energy in the active region's magnetic field, (1) that there is a sharp upper limit to the free energy the field can hold that increases with the amount of magnetic field in the active region, the active region's magnetic flux content, and (2) that most active regions are near this limit when their field explodes in a coronal mass ejection/flare eruption. That is, explosive active regions are concentrated in a main-sequence path bordering the free-energy-limit line in (flux content, free-energy proxy) phase space. Here, we present evidence that specifies the underlying magnetic condition that gives rise to the free-energy limit and the accompanying main sequence of explosive active regions. Using a suitable free-energy proxy measured from vector magnetograms of 44 active regions, we find evidence that (1) in active regions at and near their free-energy limit, the ratio of magnetic-shear free energy to the non-free magnetic energy the potential field would have is of the order of one in the core field, the field rooted along the neutral line, and (2) this ratio is progressively less in active regions progressively farther below their free-energy limit. Evidently, most active regions in which this core-field energy ratio is much less than one cannot be triggered to explode; as this ratio approaches one, most active regions become capable of exploding; and when this ratio is one, most active regions are compelled to explode.
The Principle of Stationary Action in Biophysics: Stability in Protein Folding

We conceptualize protein folding as motion in a large dimensional dihedral angle space. We use Lagrangian mechanics and introduce an unspecified Lagrangian to study the motion. The fact that we have reliable folding leads us to conjecture the totality of paths forms caustics that can be recognized by the vanishing of the second variation of the action. There are two types of folding processes: stable against modest perturbations and unstable. We also conjecture that natural selection has picked out stable folds. More importantly, the presence of caustics leads naturally to the application of ideas from catastrophe theory and allows us to consider the question of stability for the folding process from that perspective. Powerful stability theorems from mathematics are then applicable to impose more order on the totality of motions. This leads to an immediate explanation for both the insensitivity of folding to solution perturbations and the fact that folding occurs using very little free energy. The theory of folding, based on the above conjectures, can also be used to explain the behavior of energy landscapes, the speed of folding similar to transition state theory, and the fact that random proteins do not fold.
An Experimental Study on Wax Removal in Pipes With Oil Flow

Pigging is recognized as one of the most used techniques for removing wax deposits in pipelines. In an earlier paper, the mechanics of the wax removal was studied using an experimental setup under dry conditions, i.e., no oil presence. In this study, the pigging experiments are conducted for both regular disc and by-pass disc pigs under flowing conditions. A new test facility was designed and constructed. The test section is 6.1 m (20-ft) long Schedule 40 steel pipe with an inner diameter of 0.0762 m (3-in.). A mixture of a commercial wax and a mineral oil is cast inside the spool pieces for different wax thicknesses and wax oil contents. The wax breaking and plug transportation forces are investigated separately. The results indicated that the wax breaking force increases as wax thickness increases, and the wax plug transportation force gradient is independent of the wax plug length. In comparison to previous test results, presence of oil reduced the wax plug transportation force. Experimental results also showed that the wax transport behavior of the by-pass pig is significantly different than that of the regular pig. The by-pass pig allows the oil to flow through the by-pass holes and mobilizes the removed wax in front of the pig resulting in no discernible wax accumulation in front of the pig. Therefore, no measurable transportation force was observed for the by-pass pig tests.Copyright © 2007 by ASME
Transmetalation reactions of higher order cyanocuprates: Direct formation of trialkyltin cuprates from tin hydrides which bypasses organolithium intermediates

Abstract Simple exposure of n-Bu3SnH to Bu2Cu(CN)Li2 in THF at low temperatures leads directly to the presumed mixed higher order trialkyltin cuprate, the reactions of which selectively transfer the trialkylstannyl group to a variety of substrates.
Germany v. Italy and the Limits of Horizontal Enforcement Some Reflections from a United States Perspective

This contribution considers the implications of the decision of the International Court of Justice (ICJ) in Jurisdictional Immunities of the State (Germany v. Italy: Greece Intervening) for the evolution of structural norms relating to the immunity of foreign states in domestic courts, with a focus on the practice of the United States. It also considers whether the decision, which is explicitly limited to the question of state immunity, might nevertheless affect domestic courts’ willingness to recognize the immunity of officials who act on behalf of foreign states. It concludes that the state-centric nature of Germany’s challenge to Italy’s exercise of jurisdiction underscores the conceptual and doctrinal distinction between foreign state immunity, on the one hand, and foreign official immunity, on the other. This distinction is critical to legitimizing the horizontal enforcement of those substantive rules of international law that are binding on individuals and designed to protect other individuals from harms inflicted under colour of state authority.
Spring polar ozone behavior

Understanding of the springtime behavior of polar stratospheric ozone as of mid 1990 is summarized. Heterogeneous reactions on polar stratospheric clouds as hypothesis for ozone loss are considered and a simplified description of the behavior of Antarctic ozone in winter and spring is given. Evidence that the situation is more complicated than described by the theory is produced. Many unresolved scientific issues remain and some of the most important problems are identified. Ozone changes each spring since 1979 have clearly established for the first time that man made chlorine compounds influence stratospheric ozone. Long before important advances in satellite and in situ investigations, it was Dobson's decision to place a total ozone measuring spectrometer at Halley Bay in Antarctica during the International Geophysical Year and subsequent continuous monitoring which led to the discovery that ozone was being destroyed each spring by chlorine processed by polar stratospheric clouds.
Coupled basin evolution and late-stage metamorphic core complex exhumation in the southern Basin and Range Province, southeastern Arizona

Abstract Records of lithospheric extension and mountain-range uplift are most continuously contained within syntectonic sedimentary rocks in basins adjacent to large structural culminations. In southeastern Arizona, metamorphic core complexes form mountain ranges with the highest elevations in the region, and supposedly much less extended terranes lie at lower elevations. Adjacent to the Santa Catalina-Rincon metamorphic core complex, within the Tucson Basin, stratigraphic-sequence geometries evident in a large suite of 2-D seismic reflection data suggest a two-phase basin-evolution model controlled by the emplacement and subsequent uplift of the core complex. In its earliest stage, Phase I of basin formation was characterized by extensive faults forming relatively small-scale proto-basins, which coalesced with the larger basin-bounding detachment fault system. Synextensional sedimentation within the enlarging basin is evidenced by sediment-growth packages, derived from adjacent footwall material, fanning into brittle hanging-wall faults. During this phase, volcanism was widespread, and growth packages contain interbedded sediments and volcanic products but, paradoxically, no mylonitic clasts from the adjacent metamorphic core complex. Phase II of basin evolution begins after a significant tectonic hiatus and consists of a symmetric deepening of the central basin with the introduction of mylonitic clasts in the basin fill. This is coupled with the activation of a series of high-angle normal faults ringing the core complex. These observations suggest a two-phase model for metamorphic core complex evolution, with an initial stage of isostatic core complex emplacement during detachment faulting that resulted in little topographic expression. This was followed, after a significant tectonic hiatus, by late-stage exhumation and flexural uplift of the Santa Catalina-Rincon metamorphic core complex through younger high-angle faulting. Moreover, the geometry of upper basin fill units suggests an extremely low effective elastic thickness in the region and that flexural uplift of the core complex induced asymmetric transfer of ductile mid-crustal rocks from beneath the subsiding Tucson Basin to the uplifting mountain range.
Enantioselective radical reactions: the use of metal triflimides as Lewis acids

Abstract Several metal triflimides in conjunction with chiral ligands have been evaluated in conjugate radical additions. Chiral Lewis acids derived from magnesium and iron triflimides and bisoxazolines gave high enantioselectivity.
Thermodynamics of metal-organic frameworks

Although there have been extensive studies over the past decade in the synthesis and application of metal-organic frameworks (MOFs), investigation of their thermodynamic stability and of the energetics of guest–host interactions has been much more limited. This review summarizes recent progress in experimental (calorimetric) determination of the thermodynamics of MOF materials. The enthalpies of MOFs relative to dense phase assemblages suggest only modest metastability, with a general increase of enthalpy with increasing molar volume, which becomes less pronounced at higher porosity. The energy landscape of nanoporous materials (inorganic and hybrid) consists of a pair of parallel patterns within a fairly narrow range of metastability of 5–30 kJ per mole of tetrahedra in zeolites and mesoporous silicas or per mole of metal in MOFs. Thus strong thermodynamic instability does not seem to limit framework formation. There are strong interactions within the chemisorption range for small molecule–MOF interactions with defined chemical binding at the metal centers or other specific locations. Coexistence of surface binding and confinement can lead to much stronger guest–host interactions. - Graphical abstract: Energy landscape of inorganic and hybrid porous materials. - Highlights: • Thermochemical data on various MOF structures were experimentally determined. • MOFs are moderately unstable relativemore » to their dense phase assemblage. • Overall energetic landscape of porous materials was revealed. • Guest–host interactions in MOFs were evaluated directly using calorimetry. • Confinement effect and defined chemical binding lead to strong interactions.« less
GaN pnp bipolar junction transistors operated to 250 °C

The authors report on the dc performance of the first GaN pnp bipolar junction transistor. The structure was grown by MOCVD on c-plane sapphire substrates and mesas formed by low damage Inductively Coupled Plasma etching with a Cl{sub 2}/Ar chemistry. The dc characteristics were measured up to V{sub BC} of 65 V in common base mode and at temperatures up to 250 C. Under all conditions, I{sub C} {approximately} I{sub E}, indicating higher emitter injection efficiency. The offset voltage was {le} 2 V and devices were operated up to power densities of 40kW{center{underscore}dot}cm{sup {minus}2}.