cssi/SciSciGPT-SciSciNet huggingface dataset:
Commodity Futures Prices as Forecasts

Futures markets provide contemporaneous price quotations for a constellation of contracts with maturities thirty or more months in the future, and a large literature exists about interpreting these prices as forecasts. Futures markets simultaneously determine a price level and price differences appropriate to contract temporal definitions. Futures prices can efficiently reflect a complex set of factors but still provide poor forecasts. Forecasts based on quantitative models cannot, however, improve on efficient futures prices as forecasting agents; empirical models provide as poor, if not poorer, forecasts. I discuss analogous ideas for basis forecasts.
The singular geometry of the sliver

We consider ``sliver'' states which act as projection operators in the matter star product of Witten's cubic string field theory. These sliver states, which might be associated with Dp-branes, are not finite norm states in the matter string Hilbert space. We describe the singularities of these states, and demonstrate that the sliver states are composed of strings having singular geometric features. These singularities take a particularly simple form in the zero slope limit α'→0, where the star algebra factorizes into a product of the algebra of functions on space-time and the non-commutative star product of fields associated with higher string modes. An analogy to the sliver geometry suggests a natural mechanism for describing closed string states in open string field theory.
Hydrazine-mediated cyclization of Ugi products to synthesize novel 3-hydroxypyrazoles

This report discloses a novel concise synthesis of a series of 3-hydroxypyrazoles 5 via a tandem Ugi/debenzylation /hydrazine-mediated cyclization sequence. Herein, n-butyl isocyanide 4b was utilized as an alternative to classical convertible isocyanides enabling high yielding hydrazine-mediated cyclization. Taken together, a novel class of 3-hydroxypyrazoles 5a–5i was synthesized with a potential to be of interest in future library enrichment strategies.
On widening the angular existence domain for Dyakonov surface waves using the Pockels effect

The propagation of Dyakonov surface waves (DSWs) at the planar interface between an isotropic material and a linear electro-optic birefringent material can be dynamically controlled using the Pockels effect. The range of directions for DSW propagation has been previously found to be rather narrow. By careful choice of various parameters, this range of directions can be increased by more than an order of magnitude. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2360–2362, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23698
Modification and limitations of the Livinghouse catalytic Pauson-Khand reaction

Abstract The difficult and impractical purification of Co 2 (CO) 8 is not necessary in the catalytic thermal Pauson-Khand reaction previously described by Livinghouse.
Exploring the solar system galactic frontier in extreme ultraviolet

Abstract The solar system galactic frontier—the region where the expanding solar wind meets the surrounding galactic medium—remains poorly explored. The sheer size of the essentially asymmetric heliosphere calls for remote techniques to probe the properties of its global time-varying three-dimensional boundary. The Interstellar Boundary Explorer (IBEX) mission (launch in 2008) will image the region between the termination shock and the heliopause, the heliospheric sheath, in fluxes of energetic neutral atoms. Global imaging in extreme ultraviolet (EUV) will likely be the next logical step in remote exploration of the galactic frontier from 1 AU. Imaging in EUV will establish directional and spectral properties of (1) the glow of singly charged helium ( He + ) ions in the interstellar and solar wind plasmas; (2) emissions of hot plasma in the Local Bubble; and (3) characteristic emissions of the solar wind. Global imaging with ultrahigh sensitivity and ultrahigh spectral resolution will map the heliopause and reveal the three-dimensional flow pattern of the solar wind, including the flow over the Sun's poles. This article presents the emerging concept of the experiment and space mission for heliosphere global imaging in EUV.
HEAT EXCHANGER FOR IN-GROUND HEAT STORAGE

The first phase of a research project using undisturbed soil for sensible heat storage is described. A laboratory scale model of a heat exchange system was constructed and tested. Thermal charging and recovery rates, modes of heat transport and transient temperature conditions, as well as over-all heat storage performance of the unit are given. The experimental results are compared with predictions of a numerical model based on mass and heat transport. A prototype field installation has been constructed and preliminary results are presented.
Practical uses of synchronized clocks in distributed systems

Synchronized clocks are interesting because they can be used to improve performance of a distributed system by reducing communication. Since they have only recently become a reality in distributed systems, their use in distributed algorithms has received relatively little attention. This paper discusses a number of distributed algorithms that make use of synchronized clocks and analyzes how clocks are used in these algorithms.
Negative correlation and log-concavity

We give counterexamples and a few positive results related to several conjectures of R. Pemantle (Pemantle, J Math Phys 41 (2000), 1371–1390) and D. Wagner (Wagner, Ann Combin 12 (2008), 211–239) concerning negative correlation and log-concavity properties for probability measures and relations between them. Most of the negative results have also been obtained, independently but somewhat earlier, by Borcea et al. (Borcea et al., J Am Math Soc 22 (2009), 521–567). We also give short proofs of a pair of results from (Pemantle, J Math Phys 41 (2000), 1371–1390) and (Borcea et al., J Am Math Soc 22 (2009), 521–567); prove that “almost exchangeable” measures satisfy the “Feder-Mihail” property, thus providing a “non-obvious” example of a class of measures for which this important property can be shown to hold; and mention some further questions. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2010
On bending angles by gravitational lenses in motion

The bending of light rays by the gravitational field of a 'lens' that is moving relative to the observer is calculated within the approximation of weak fields, small angles and thin lenses. Up to first order in v/c (and assuming the acceleration to be much smaller than v/c), the bending angle, time delay and redshift of the images are found to be affected by the component of the speed of the deflector along the line of sight. The correction takes the form of an overall factor of 1 + v/c accompanying the mass of the deflector, leading to an indeterminacy of the order of v/c in the mass of the lens inferred on the basis of the separation of multiple images. The consequent correction to the microlensing light curve is pointed out, as well as scenarios where the correction is potentially relevant.
Equilibrium evolution on the resistive time scale in a tokamak reactor

In the Engineering Test Facility (ETF), the plasma pulse duration is expected to be hundreds of seconds, which is comparable to the resistive time scale that governs the resistive diffusion of the equilibrium. The resistive evolution of the safety factorq profile may, for MHD stability reasons, limit the duration of the plasma burn in a tokamak reactor. It may be possible to control this evolution and extend the plasma burn time through proper profile tailoring. We study the evolution of theq profile on the resistive time scale numerically using a one- and-one-half-dimensional (1 1/2-D) single fluid transport code. Two high beta (βT ∼ 7–16%) cases are considered: (a) a beam-driven hydrogen plasma with no nuclear alpha heating for which the beam energy is used as a device to control the temperature profile, and (b) an ignited D-T plasma in which the neutral injection has been turned off. For the beam-driven plasma, it is shown that low beam energy heating profiles lead to resistive steady states having broad temperature profiles and flatq profiles, while high beam energy heating profiles lead to resistive steady states having peaked temperature profiles and deepq profiles. The centralized nuclear heating in an ignited D-T plasma causes the evolution of theq profile for this case to behave much like that in the high energy, beam-driven case: namely, theq values near the plasma center decrease on the resistive time scale until a deep, resistive, steady-stateq profile is reached.
Crystal Growth of a New Series of Complex Niobates, LnKNaNbO5 (Ln = La, Pr, Nd, Sm, Eu, Gd, and Tb): Structural Properties and Photoluminescence

Single crystals of LnKNaNbO5 (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) were grown out of a reactive high temperature hydroxide melt. The structures were solved by single crystal X-ray diffraction. All compounds of the series LnKNaNbO5 crystallize in the space group P4/nmm. The niobium is located in a rare square pyramidal coordination environment in this layered structure. EuKNaNbO5, GdKNaNbO5, and TbKNaNbO5 exhibit room temperature photoluminescence with bright orange-red, pink-purple, and green emissions, respectively. Unlike in many oxide structures, the photoluminescence is not quenched, although the rare earth elements fully occupy a position in the crystal structure.
Social Class, Political Power, and the State and Their Implications in Medicine:

This three-part article presents an analysis of the distribution of power and of the nature of the state in Western industrialized societies, and details their implications in medicine. Part I pres...
Decoupled access/execute computer architectures

An architecture for improving computer performance is presented and discussed. The main feature of the architecture is a high degree of decoupling between operand access and execution. This results in an implementation which has two separate instruction streams that communicate via queues. A similar architecture has been previously proposed for array processors, but in that context the software is called on to do most of the coordination and synchronization between the instruction streams. This paper emphasizes implementation features that remove this burden from the programmer. Performance comparisons with a conventional scalar architecture are given, and these show that considerable performance gains are possible.Single instruction stream versions, both physical and conceptual, are discussed with the primary goal of minimizing the differences with conventional architectures. This would allow known compilation and programming techniques to be used. Finally, the problem of deadlock in such a system is discussed, and one possible solution is given.
Trends in the prevalence and mortality of cognitive impairment in the United States: Is there evidence of a compression of cognitive morbidity?

Background Recent medical, demographic, and social trends might have had an important impact on the cognitive health of older adults. To assess the impact of these multiple trends, we compared the prevalence and 2-year mortality of cognitive impairment (CI) consistent with dementia in the United States in 1993 to 1995 and 2002 to 2004. Methods We used data from the Health and Retirement Study (HRS), a nationally representative population-based longitudinal survey of U.S. adults. Individuals aged 70 years or older from the 1993 (N = 7,406) and 2002 (N = 7,104) waves of the HRS were included. CI was determined by using a 35-point cognitive scale for self-respondents and assessments of memory and judgment for respondents represented by a proxy. Mortality was ascertained with HRS data verified by the National Death Index. Results In 1993, 12.2% of those aged 70 or older had CI compared with 8.7% in 2002 (P < .001). CI was associated with a significantly higher risk of 2-year mortality in both years. The risk of death for those with moderate/severe CI was greater in 2002 compared with 1993 (unadjusted hazard ratio, 4.12 in 2002 vs 3.36 in 1993; P = .08; age- and sex-adjusted hazard ratio, 3.11 in 2002 vs 2.53 in 1993; P = .09). Education was protective against CI, but among those with CI, more education was associated with higher 2-year mortality. Conclusions These findings support the hypothesis of a compression of cognitive morbidity between 1993 and 2004, with fewer older Americans reaching a threshold of significant CI and a more rapid decline to death among those who did. Societal investment in building and maintaining cognitive reserve through formal education in childhood and continued cognitive stimulation during work and leisure in adulthood might help limit the burden of dementia among the growing number of older adults worldwide.
Iridium catalyzed enantioselective hydrogenation of α-alkoxy and β-alkoxy vinyl ethers

Iridium catalyzed, enantioselective hydrogenations of functionalized, acid-sensitive vinyl ethers are reported. These reactions are mediated by the chiral N-carbene–oxazoline complex 1 that, unlike similar N,P-ligated catalysts (6 and 7), gives hydrogenation products (with enantioselectivities up to 96%) without significant acid-mediated degradation. In general, higher enantioselectivities were observed for the allylic alcohol derivatives (2) than the α-methoxycinnamate-based compounds (4).
Repairable Fountain Codes

We introduce a new family of Fountain codes that are systematic and also have sparse parities. Given an input of k symbols, our codes produce an unbounded number of output symbols, generating each parity independently by linearly combining a logarithmic number of randomly selected input symbols. The construction guarantees that for any e>0 accessing a random subset of (1+e)k encoded symbols, asymptotically suffices to recover the k input symbols with high probability. Our codes have the additional benefit of logarithmic locality: a single lost symbol can be repaired by accessing a subset of O(log k) of the remaining encoded symbols. This is a desired property for distributed storage systems where symbols are spread over a network of storage nodes. Beyond recovery upon loss, local reconstruction provides an efficient alternative for reading symbols that cannot be accessed directly. In our code, a logarithmic number of disjoint local groups is associated with each systematic symbol, allowing multiple parallel reads. Our main mathematical contribution involves analyzing the rank of sparse random matrices with specific structure over finite fields. We rely on establishing that a new family of sparse random bipartite graphs have perfect matchings with high probability.
Lambert Targeting for On-Orbit Delivery of Debris Remediation Dust

Tungsten dust used as an artificial atmosphere to aid in deorbiting of space debris should be deployed soon after a fragmentation to be effective, before the delta-v imparted to each fragment and orbit perturbations spreads the debris so far apart that an impractically large amount of dust must be used. Maneuvering a spacecraft carrying a sufficient amount of dust and launched in advance of need is one way of reaching the target region quickly; the question addressed here is whether a significant fraction of possible fragmentations can be reached with a vehicle with a realistic fuel capacity. Lambert targeting is computed to reach the point of need at the correct elapsed time from the dispatch time and place. The time delay may be varied above some presumed minimum needed for fragmentation detection, communication, and maneuver initiation. With more than one vehicle on orbit, the fraction of fragmentations reachable in the requisite time increases. With just two vehicles, it is possible to reach 69% of or...
Mixed state estimation for a linear Gaussian Markov model

We consider a discrete-time dynamical system with Boolean and continuous states, with the continuous state propagating linearly in the continuous and Boolean state variables, and an additive Gaussian process noise, and where each Boolean state component follows a simple Markov chain. This model, which can be considered a hybrid or jump-linear system with very special form, or a standard linear Gauss-Markov dynamical system driven by a Boolean Markov process, arises in dynamic fault detection, in which each Boolean state component represents a fault that can occur. We address the problem of estimating the state, given Gaussian noise corrupted linear measurements. Computing the exact maximum a posteriori (MAP) estimate entails solving a mixed integer quadratic program, which is computationally difficult in general, so we propose an approximate MAP scheme, based on a convex relaxation, followed by rounding and (possibly) further local optimization. Our method has a complexity that grows linearly in the time horizon and cubicly with the state dimension, the same as a standard Kalman filter. Numerical experiments suggest that it performs very well in practice.
Problems involved in understanding orders of nucleophilic reactivity

Abstract The N + relationship has been found to have considerable generality for the correlation of rate constants of electrophile-nucleophile combination reactions. There are, however, some serious deviations from the relationship, particularly for thiolate anions and for azide ion reactions. Data for a large number of reactions show an absence of selectivity-reactivity relationships and a general absence of observable coulombic effects. Detailed examination of the data by the use of the N + relationship reveals some examples of apparent steric effects on reactivity which, in the case of secondary amines, cause deviations of up to ca. 1 log unit. The deviant behavior of thiolate and azide ions do not appear to be rationalizable by any of the current theories of nucleophilic reactivity.
Tumor cell migration in complex microenvironments

Tumor cell migration is essential for invasion and dissemination from primary solid tumors and for the establishment of lethal secondary metastases at distant organs. In vivo and in vitro models enabled identification of different factors in the tumor microenvironment that regulate tumor progression and metastasis. However, the mechanisms by which tumor cells integrate these chemical and mechanical signals from multiple sources to navigate the complex microenvironment remain poorly understood. In this review, we discuss the factors that influence tumor cell migration with a focus on the migration of transformed carcinoma cells. We provide an overview of the experimental and computational methods that allow the investigation of tumor cell migration, and we highlight the benefits and shortcomings of the various assays. We emphasize that the chemical and mechanical stimulus paradigms are not independent and that crosstalk between them motivates the development of new assays capable of applying multiple, simultaneous stimuli and imaging the cellular migratory response in real-time. These next-generation assays will more closely mimic the in vivo microenvironment to provide new insights into tumor progression, inform techniques to control tumor cell migration, and render cancer more treatable.
A novel protecting strategy for internucleosidic phosphate and phosphorothioate groups.

The utility of 2–(N–isopropyl–N–anisoylamino)ethyl group for protection of internucleosidic phosphate linkages in oligonucleotide synthesis was studied. The group demonstrated high coupling yields, favorable deprotection kinetics and a high hydrolytic stability of phosphoramidite building blocks. The mechanism of deprotection was established using a model phosphate triester.
Unusual regiochemistry in the hydroboration of 3,3-dibenzylcycloalkenes

Abstract Reaction of 3,3-dibenzylcycloalkenes with diborane results in predominant attack by boron at the more crowded ends of the double bonds.
Photoreduction of 99Tc Pertechnetate by Nanometer-Sized Metal Oxides: New Strategies for Formation and Sequestration of Low-Valent Technetium

Technetium-99 (99Tc) (β–max: 293.7 keV; t1/2: 2.1 × 105 years) is a byproduct of uranium-235 fission and comprises a large component of radioactive waste. Under aerobic conditions and in a neutral–basic environment, the pertechnetate anion (99TcO4–) is stable. 99TcO4– is very soluble, migrates easily through the environment and does not sorb well onto mineral surfaces, soils, or sediments. This study moves forward a new strategy for the reduction of 99TcO4– and the chemical incorporation of the reduced 99Tc into a metal oxide material. This strategy employs a single material, a polyoxometalate (POM), α2-[P2W17O61]10–, that can be photoactivated in the presence of 2-propanol to transfer electrons to 99TcO4– and incorporate the reduced 99Tc covalently into the α2-framework to form the 99TcVO species, 99TcVO(α2-P2W17O61)7–. This occurs via the formation of an intermediate species that slowly converts to 99TcVO(α2-P2W17O61)7–. Extended X-ray absorption fine structure and X-ray absorption near-edge spectroscop...
A portrait of the torus as a disk-driven hydromagnetic wind

Abstract Centrifugally driven winds originating from the surfaces of magnetized accretion disks in AGNs possess unique observational characteristics owing to their highly stratified structure and their exposure to the central engine's radiation field. The obscuration and radiation properties of such winds may provide the physical basis for the dusty tori invoked in various AGN unification schemes. We discuss the angular-dependent optical and X-ray properties of such winds, their infrared emission, and their capacity to polarize the central source continuum spectrum via electron/dust scattering and dichroic extinction by magnetically aligned grains.
Catalytic effect of alkali carbonates on the calcination of calcium carbonate

Abstract Alkali carbonates (except for francium carbonate) have been tested to enhance the calcination of calcium carbonate using a Lindberg furnace and a differential thermal analysis/thermogravimetric analysis (DTA-TGA) system. The alkali carbonates were mixed with calcium carbonate (calcite) at a weight ratio of 1:20 and were studied at constant temperatures of 800 and 700 °C in a Lindberg furnace and a DTA-TGA analyzer, respectively. The results of calcination rates (wt% h−1) from the Lindberg furnace and DTA-TGA analyzer have shown similarly that lithium carbonate is the best catalyst among the alkali carbonates.
Connecting the dots: using sunlight to drive electrochemical oxidations

Inexpensive, readily available photovoltaic cells have been used to conduct electrochemical oxidation reactions. In this way, the energy efficiency of sunlight-driven reactions can be combined with the versatility of electrochemistry to create new, sustainable methods for conducting oxidation reactions.
Leakage-resilient coin tossing

The ability to collectively toss a common coin among $$n$$ n parties in the presence of faults is an important primitive in the arsenal of randomized distributed protocols. In the case of dishonest majority, it was shown to be impossible to achieve less than $$\frac{1}{r}$$ 1 r bias in $$O(r)$$ O ( r ) rounds (Cleve STOC '86). In the case of honest majority, in contrast, unconditionally secure $$O(1)$$ O ( 1 ) -round protocols for generating common perfectly unbiased coins follow from general completeness theorems on multi-party secure protocols in the perfectly secure channels model (e.g., BGW, CCD STOC '88). However, in the multi-party protocols with honest majority, parties must generate and hold local secret values which are assumed to be perfectly hidden from malicious parties: an assumption which is crucial to proving the resulting common coin is unbiased. This assumption unfortunately does not seem to hold in practice, as attackers can launch side-channel attacks on the local state of honest parties and leak information on their secrets. In this work, we present an $$O(1)$$ O ( 1 ) -round protocol for collectively generating an unbiased common coin, in the presence of leakage on the local state of the honest parties. We tolerate $$t \le (\frac{1}{3} - \epsilon ) n$$ t ≤ ( 1 3 - ∈ ) n computationally unbounded statically scheduled Byzantine faults and in addition a $$\varTheta (1)$$ ? ( 1 ) -fraction leakage on each (honest) party's secret state. Our results hold in the memory leakage model (of Akavia, Goldwasser, Vaikuntanathan '08) adapted to the distributed setting. Another contribution of our work is a tool we use to achieve collective coin flipping—leakage-resilient verifiable secret sharing (VSS). Informally, this is a variant of ordinary VSS in which secrecy guarantees are maintained even if information is leaked on individual shares of the secret.
The Role of the Interstellar Medium in Galaxy Formation Simulations

There is a strong connection between the formation of a disk galaxy and the properties of the interstellar medium (ISM). Theoretical work has typically either focused on the cosmological buildup of a galaxy with a relatively crude model for the gas physics, or examined local processes in the ISM and ignored the global evolution of the galaxy itself. Here, I briefly review what has been learned from both of these approaches, and what can be done to bridge the gap between them. I argue that cosmological simulations need to learn from observational and theoretical work on local ISM properties and adopt more sophisticated models for the processes that they cannot resolve. Since the ISM is still incompletely understood, there are a number of reasonable approaches for these “subgrid" models, and I will discuss the strengths and limitations of each.
Review of recent measurements in the top quark sector at the Tevatron

Recent measurements in the top quark sector at the Fermilab Tevatron collider are discussed. Measurements at the Tevatron use up to 9.7 fb-1 of data corresponding to the full data sets recorded by each of the experiments, CDF and DO. This review discusses the most recent measurements of inclusive and differential top quark cross-sections in strong and electroweak production of top quarks and related measurements, as well as measurements of angular distributions related to asymmetries in top quark production. Furthermore, the current status of precision measurements of the mass of the top quark is discussed. Where available, combinations of CDF and DO results are presented.
Mechanism of the Very Efficient Quenching of Tryptophan Fluorescence in Human γD- and γS-Crystallins: The γ-Crystallin Fold May Have Evolved To Protect Tryptophan Residues from Ultraviolet Photodamage†

Proteins exposed to UV radiation are subject to irreversible photodamage through covalent modification of tryptophans (Trps) and other UV-absorbing amino acids. Crystallins, the major protein components of the vertebrate eye lens that maintain lens transparency, are exposed to ambient UV radiation throughout life. The duplicated β-sheet Greek key domains of β- and γ-crystallins in humans and all other vertebrates each have two conserved buried Trps. Experiments and computation showed that the fluorescence of these Trps in human γD-crystallin is very efficiently quenched in the native state by electrostatically enabled electron transfer to a backbone amide [Chen et al. (2006) Biochemistry 45, 11552−11563]. This dispersal of the excited state energy would be expected to minimize protein damage from covalent scission of the excited Trp ring. We report here both experiments and computation showing that the same fast electron transfer mechanism is operating in a different crystallin, human γS-crystallin. Exami...
On the decay of crossing numbers

The crossing number cr(G) of a graph G is the minimum number of crossings over all drawings of G in the plane. In 1993, Richter and Thomassen [B. Richter, C. Thomassen, Minimal graphs with crossing number at least k, J. Combin. Theory Ser. B 58 (1993) 217-224] conjectured that there is a constant c such that every graph G with crossing number k has an edge e such that cr(G-e)>=k-ck. They showed only that G always has an edge e with cr(G-e)>=25cr(G)-O(1). We prove that for every fixed @e>0, there is a constant n"0 depending on @e such that if G is a graph with n>n"0 vertices and m>n^1^+^@e edges, then G has a subgraph G^' with at most ([email protected])m edges such that cr(G^')>=(128-o(1))cr(G).
An unusual stereochemical directing effect of propargylic oxygen substituents on an intramolecular Diels-Alder reaction

Abstract Varying the substituent on the oxygen of a propargylic alcohol affects the stereochemical course of an intramolecular Diels-Alder reaction of a diene-yne.
Tandem radical cyclizations promoted by O-stannyl ketyls

Abstract This work summarizes an investigation of tandem radical cyclizations triggered by O-stannyl ketyls. This organometallic reactive intermediate is prepared from the reaction of tributyltin hydride (nBu3SnH) with a carbonyl functional group by a free radical chain mechanism. Several precursor substrates leading to “separated,” “spiro,” and “fused” cyclopentaniod ring systems were investigated which collectively have good synthetic potential for the construction of a wide array of substituted polycyclic products.
Intramolecular metal catalyzed Kharasch cyclizations of olefinic α-halo esters and acids

Abstract Functionalized carbocyclic compounds are produced by intramolecular Kharasch radical cyclization reactions catalyzed by various transition metal complexes. Several unsaturated mono-α-haloesters and acids can be efficiently transformed to γ-halocarboxyl and γ-lactone carbocycles via exo closure of a 5-hexenyl type radical intermediate. The cyclization methodology is useful for synthesis of both fused and bridged carbocycles.
Thermal convection in an enclosure due to vibrations aboard spacecraft

This paper discusses thermal convection in an enclosure induced by spacecraft vibrations (#-jitter). Under normal circumstances (no maneuvers, no intentional spinning of the spacecraft) the ^-jitter generates predominantly oscillatory velocity and temperature fields with zero time-mean values. The ^-jitter can also generate secondary flows with nonzero mean, but they are of much smaller order. Some implications of the g- jitter on materials processing in space are discussed. NE of the primary advantages foreseen for processing of materials in space is the reduction of natural convection associated with the Earth's gravity. However, there have been some indications (e.g., Apollo 14 experiments 1'2) that spacecraft vibrations might cause appreciable thermal con- vection. Such convection may be important in fluids ex- periments and also affect the quality of crystals grown in space. Therefore, to study the effectiveness of spacecraft vibrations in generating fluid flows, the present work theoretically investigates a case in which a fluid-filled con- tainer with differentially heated walls is subjected to spacecraft vibrations. Implications of the results for space processing are discussed. In an attempt to evaluate the effects of g-jitter on fluid motions Spradley el al. 3 made a numerical analysis for various configurations. They considered three g-jitter profiles, sinusoidal, absolute sinusoidal and saw tooth, and compared the flowfields with that for constant g level. They found that if the g-jitter is decomposed into a time mean part and an oscillatory part, the mean part is more important than the oscillatory part in determining the flowfield and heat- transfer rate. A somewhat related work has been done by Forbes4 where the effect of sinusoidal vibrations on natural convective heat transfer in a rectangular enclosure is studied experimentally as well as numerically under 1-g conditions. The results indicate that the vibrations have very little effect on the heat transfer when the flow is laminar. The present study is more comprehensive than the work by Spradley et al.,3 and is meant to give a better physical insight into the g-jitter in space. Some of the material presented herein is taken from the work by Prasad and Ostrach.5 Formulation of the Problem g-Jitter Consider an experimental setup which is in a spaceship orbiting the Earth (Fig. 1). The coordinates (X0,Y0,Z0) are fixed at the center of the Earth with origin 0 (fixed frame of reference), and the coordinates (X'f Y',Z') are attached to the spacecraft with origin 0' at its center of mass. The coor-
Electronic and solvent effects in the reaction of zinc porphyrins with a metal imidazolate complex or 1-methylimidazole

Abstract The reactions of Zn(p-XTPP) derivatives (X = CF3, Cl, F, H, CH3, OCH3, N(Et)2) with a copper imidazolate complex to yield imidazolate bridged binuclear axial adducts to the porphyrin were followed in the visible region between 700–450 nm. The α and β bands of the porphyrin shift to lower energy and the ϵβ/ϵα ratio decreases upon adduct formation. Equilibrium constants for the reaction were measured in toluene at 25.3 °C using the β band maximum of the parent zinc porphyrin. A plot of log Keq with the Hammett constant is linear with a slope of 0.208, which indicates that the formation of the binuclear adducts is aided by electron with drawing substituents on the porphyrin. Replacement of the copper atom in the imidazolate complex with nickel significantly reduces the value of Keq for the reaction with Zn(TPP) while the free ligand fails to react at all. The reduced reactivity with the nickel imidazolate complex is attributed to entropy effects and that of the non-reacting metal free complex to conformational effects. Equilibrium constants for the reaction of N-CH3Im with Zn(TPP) conducted in dichloromethane, toluene, dimethoxyethane, and dimethylsulfoxide reveal a linear dependence of log Keq on the position of the α or β in a given solvent. The relative ordering of Keq in various solvents is given by the position of the α or β band maximum of the parent zinc porphyrin. The lower the energy of the bands the smaller the value of Keq.
Asymmetric synthesis of anti-β-hydroxy-α-amino acids

Abstract The stereoselective aldol addition reactions of chiral haloacetate enolates is reported. The conversion of these adducts to enantiomerically pure anti-β-hydroxy-α-amino acids is demonstrated (Eq 2).
Effect of doping on the strength and infrared transmittance of hot-pressed cesium iodide

The effect of additions of other iodide materials on the mechanical strength and optical transmittance of polycrystalline CsI was investigated. Divalent or trivalent iodides were unsuitable as dopant materials because they tended to decrease transmittance in the extreme infrared region. However, significant increases in transmittance as well as in strength were observed when polycrystalline CsI was doped with small amounts of monovalent iodide materials, especially with AgI. In the case of AgI, the increases in strength and transmittance were attributed to the pinning of grain boundaries and, therefore, the inhibition of grain growth during hot-pressing, resulting in a material having much smaller grains. The maximum fracture strength obtained in this study (in CsI doped with 0.05 mol% of AgI, and pressed for 1 h at 150{degrees}C and a pressure of 103 MPa) was 40 MPa, which is about 4 times higher than that of an undoped sample and {approximately}10 times higher than that of pure single-crystal CsI. The samples with maximum strength also exhibited the optimum optical transmittance.
Optimal channel probing and transmission scheduling for opportunistic spectrum access

In this study, we consider optimal opportunistic spectrum access (OSA) policies for a transmitter in a multichannel wireless system, where a channel can be in one of multiple states. In such systems, the transmitter typically does not have complete information on the channel states, but can learn by probing individual channels at the expense of certain resources, e.g., energy and time. The main goal is to derive optimal strategies for determining which channels to probe, in what sequence, and which channel to use for transmission. We consider two problems within this context and show that they are equivalent to different data maximization and throughput maximization problems. For both problems, we derive key structural properties of the corresponding optimal strategy. In particular, we show that it has a threshold structure and can be described by an index policy. We further show that the optimal strategy for the first problem can only take one of three structural forms. Using these results, we first present a dynamic program that computes the optimal strategy within a finite number of steps, even when the state space is uncountably infinite. We then present and examine a more efficient, but suboptimal, two-step look-ahead strategy for each problem. These strategies are shown to be optimal for a number of cases of practical interest. We examine their performance via numerical studies.
Underlying Consumer Heterogeneity in Markets for Subscription-Based IT Services with Network Effects

In this paper we explore the underlying consumer heterogeneity in competitive markets for subscription-based information technology services that exhibit network effects. Insights into consumer heterogeneity with respect to a given service are paramount in forecasting future subscriptions, understanding the impact of price and information dissemination on market penetration growth, and predicting the adoption path for complementary products that target the same customers as the original service. Employing a continuous-time utility model, we capture the behavior of a continuum of consumers who are differentiated by their intrinsic valuations from using the service. We study service subscription patterns under both perfect and imperfect information dissemination. In each case, we first specify the conditions under which consumer rational behavior supported by the utility model can explain a general observed adoption path, and if so, we explicitly derive the analytical closed-form expression for the consumer valuation distribution. We further explore the impact of awareness and distribution skewness on adoption. In particular, we highlight the practical forecasting importance of understanding the information dissemination process in the market as observed past adoption may be explained by several distinct awareness and heterogeneity scenarios that may lead to divergent adoption paths in the future. Moreover, we show that in the later part of the service lifecycle the subscription decision for new customers can be driven predominantly by information dissemination instead of further price markdowns. We also extend our results to time-varying consumer valuation scenarios. Furthermore, based on our framework, we advance a set of heuristic methods to be applied to discrete-time real industry data for estimation and forecasting purposes. In an empirical exercise, we apply our methodology to the Japanese mobile voice services market and provide relevant managerial insights from the analysis.
Effects of jurors’ gender and attitudes toward intellectual disability on judgments in cases involving disabled juvenile defendants

Because many juvenile offenders are intellectually disabled and have their cases tried by jurors in adult criminal court, it is important to understand factors that influence jurors’ judgments in such cases. Using a mock trial methodology, we explored the relations among jurors’ gender, attitudes toward intellectual disability, and judgments in a criminal case involving an intellectually disabled 15-year-old girl accused of murder. Men mock jurors’ judgments were not influenced by their preexisting biases, but women's were: the more women favored special treatment for disabled offenders, the less likely they were to suspect the disabled juvenile was guilty and the less likely they were to convict her. Implications for actual cases involving disabled juvenile defendants are discussed.
National Geospatial-Intelligence Agency Academic Research Program

"Know the Earth... Show the Way". In fulfillment of its vision, the National Geospatial-Intelligence Agency (NGA) provides geospatial intelligence in all its forms and from whatever source - imagery, imagery intelligence, and geospatial data and information - to ensure the knowledge foundation for planning, decision, and action. To achieve this, NGA conducts a multi-disciplinary program of basic research in geospatial intelligence topics through grants and fellowships to the leading investigators, research universities, and colleges of the nation. This research provides the fundamental science support to NGA's applied and advanced research programs. The major components of the NGA Academic Research Program (NARP) are the NGA University Research Initiatives (NURI), the Historically Black College and University - Minority Institution Research Initiatives (HBCU-MI), the service Academy Research Grants, and the director of Central Intelligence Post-Doctoral Research Fellowships
A case study of large-scale structure in a 'hot' model universe

Large-scale structure is studied in an Omega(0) = 1 model universe filled with 'hot' dark matter. A particle mesh computer code is used to calculate the development of gravitational instabilities in 64-cubed mass clouds on a 64-cubed three-dimensional grid over an expansion factor of about 1000. The present epoch is identified by matching the slope of the model particle-particle two-point correlation function with that obtained from observations of galaxies, and the model then corresponds to a cubical sample of the universe of about 105/h Mpc on a side. Properties of the simulated universe are investigated by casting the model quantities into observer's coordinates and comparing the results with observations of the spatial and velocity distributions of luminous matter. It is concluded based on simple arguments that current limits on the time of galaxy formation do not rule out 'hot' dark matter.
New electrical potential method for measuring crack growth in nonconductive materials

Abstract DC electric potential technique has been used to monitor crack growth in conductive materials. A constant DC current is passed through these materials and the crack length is measured through the changes in the electrical voltage at the crack mouth. However, this method is not applicable in crack growth measurement in nonconductive materials or adhesively bonded joints. For these materials, a new method is developed and is shown to provide a very accurate method for measuring the crack length. The surface of these materials is coated with a thin layer of carbon paint and the crack length is measured through the changes in the electrical resistance of the carbon paint, as the crack grows both in the base material and the thin layer carbon paint. In contrast to the DC electric potential technique where the position of the probes for measuring the crack length is very important for an accurate measurement of the crack length, the new technique is little sensitive to the probe location. Crack growth is measured in adhesively bonded joints subjected to creep loadings. A modified compact tension specimen is cut in two pieces across its notch area. The pieces are then glued using an adhesive. The surface of the specimen is painted with a thin layer of carbon paint and the changes in its electrical resistance are monitored. It is shown that the carbon paint method provides a quiet sensitive method for monitoring the crack growth. The creep crack growth rate in the adhesively bonded joint is related to Mode I energy release rate, G1. It is shown that the crack grows in the middle of the adhesive layer rather than at the interface of the joint. Micro-mechanisms of the crack growth are studied using a scanning electron microscope. The damage consists of numerous crazed regions at the crack tip. Crack grows by the linkage of the crazed region.
Group rekeying with limited unicast recovery

In secure group communications, a key server can deliver a "group-oriented" rekey message [C.K. Wong, M.G. Gouda, S.S. Lam, Secure group communications using key graphs, in: Proceedings of ACM SIGCOMM '98, September 1998, pp. 68-79] to a large number of users efficiently using multicast. For reliable delivery, Keystone [C.K. Wong, S.S. Lam, Keystone: a group key management system, in: Proceedings of International Conference on Telecommunications, Acapulco, Mexico, May 2000] proposed the use of forward error correction (FEC) in an initial multicast, followed by the use of unicast delivery for users that cannot recover their new keys from the multicast. In this paper, we investigate how to limit unicast recovery to a small fraction r of the user population. By specifying a very small r, almost all users in the group will receive their new keys within a single multicast round.We present analytic models for deriving r as a function of the amount of FEC redundant information (denoted by h) and the rekeying interval duration (denoted by T) for both Bernoulli and two-state Markov Chain loss models. From our analyses, we conclude that r decreases roughly at an exponential rate as h increases. We then present a protocol designed to adaptively adjust (h, T) to achieve a specified r. In particular, our protocol chooses from among all feasible (h, T) pairs one with h and T values close to their feasible minima. Our protocol also adapts to an increase in network traffic. Simulation results using ns-2 show that with network congestion our adaptive FEC protocol can still achieve a specified r by adjusting values of h and T.
The action of S_n on the cohomology of M_{0,n}(R)

In recent work by Etingof, Henriques, Kamnitzer, and the author, a presentation and explicit basis was given for the rational cohomology of the real locus \(\overline{M}_{0,n}({\mathbb{R}})\) of the moduli space of stable genus 0 curves with n marked points. We determine the graded character of the action of Sn on this space (induced by permutations of the marked points), both in the form of a plethystic formula for the cycle index, and as an explicit product formula for the value of the character on a given cycle type.
Synthesis of Metastable Phases in the Magnesium Spinel−Alumina System

We report here the use of liquid-feed flame spray pyrolysis to produce 14 nanopowders along the Al2O3−MgAl2O4 tie-line by combusting varied ratios of aerosolized ethanol solutions of alumatrane [Al(OCH2CH2)3N] and magnesium acetylacetonate [Mg(C5H7O2)2]. The resulting nanopowders were characterized by X-ray fluorescence, N2 adsorption (Brunauer−Emmett−Teller), scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The powders typically consist of single-crystal particles of <30 nm diameter and specific surface areas of 30–80 m2/g. Complementary XRD and FTIR studies show a gradual change in the powder patterns and spectra from δ-Al2O3 to MgAl2O4. Intermediate compositions exhibit phases that fall well outside of the established phase diagram and provide insight into the structure of transition aluminas. These materials have been shown to exhibit novel photonic behavior and have potential value as a new catalyst or support.
Bubbles and constraints on debt accumulation

It is commonly thought (Tirole, Econometrica 50 (1982), 1163–1182) that bubbles cannot occur in deterministic sequential market economies with a finite number of infinitely lived agents. This paper shows that the constraint on debt accumulation which make possible the existence of equilibrium can cause bubbles. If agents face a wealth constraint, bubbles can exist if and only if the assest is in zero net supply. If agents face exogenous short sales constraints, bubbles can exists if and only if some agent's endowment grows at a rate larger than the rate of return and the short sales constraint binds that agent infinitely often.
Classification of Pointed Hopf Algebras of Dimension p 2 over any Algebraically Closed Field

Let p be a prime. We complete the classification of pointed Hopf algebras of dimension p 2 over an algebraically closed field k. When char k ≠ p, our result is the same as the well-known result for char k = 0. When char k = p, we obtain 14 types of pointed Hopf algebras of dimension p 2, including a unique noncommutative and noncocommutative type.