cssi/SciSciGPT-SciSciNet huggingface dataset:
Electronic interactions between gold nanoclusters in constrained geometries

The interactions between gold nanoclusters dispersed in decane $({\mathrm{C}}_{10}{\mathrm{H}}_{22})$ when confined in narrow gaps of a few nanometers were investigated. The diameter of the gold core was $1.8\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. The clusters were capped off with alkanethiol molecules of different lengths (${\mathrm{C}}_{6}\mathrm{S}$ and ${\mathrm{C}}_{15}\mathrm{S}$) to prevent metallic contact with each other. By applying force to the gap walls, the cluster suspension was squeezed out of the gap in a nearly continuous way. In the case of the shorter ligand ${\mathrm{C}}_{6}\mathrm{S}$, the width of the minimum gap at the highest applied force was $7\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ ($\ensuremath{\sim}3$ cluster diameters). In contrast with the continuous decrease in thickness, the gap capacitance exhibited stepwise increases, which are interpreted as Mott type insulator-to-metal transition of aggregates of clusters under pressure when the average distance between the metallic cores becomes less than $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. With longer ligands, ${\mathrm{C}}_{15}\mathrm{S}$, the thickness of the minimum gap was $12\char21{}15\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. In that case, no discontinuous steps in thickness or capacitance were observed, showing that the longer ligand effectively prevents exchange interactions between the metallic cores of the nanoclusters.
Results and Implications of a 12-Year Longitudinal Study of Science Concept Learning

This paper describes the methods and outcomes of a 12-year longitudinal study into the effects of an early intervention program, while reflecting back on changes that have occurred in approaches to research, learning and instruction since the preliminary inception stages of the study in the mid 1960s. We began the study to challenge the prevailing consensus at the time that primary school children were either preoperational or concrete operational in their cognitive development and they could not learn abstract concepts. Our early research, based on Ausubelian theory, suggested otherwise. The paper describes the development and implementation of a Grade 1–2 audio tutorial science instructional sequence, and the subsequent tracing over 12 years, of the children’s conceptual understandings in science compared to a matched control group. During the study the concept map was developed as a new tool to trace children’s conceptual development. We found that students in the instruction group far outperformed their non-instructed counterparts, and this difference increased as they progressed through middle and high school. The data clearly support the earlier introduction of science instruction on basic science concepts, such as the particulate nature of matter, energy and energy transformations. The data suggest that national curriculum standards for science grossly underestimate the learning capabilities of primary-grade children. The study has helped to lay a foundation for guided instruction using computers and concept mapping that may help both teachers and students become more proficient in understanding science.
Circulation through the Central American Seaway during the Miocene carbonate crash

Changes in circulation associated with the shoaling of the Isthmus of Panama and the Caribbean carbonate crash in the Miocene were investigated using Nd isotopes from fossil fish teeth and debris from two sites in the Caribbean Basin (Ocean Drilling Program Sites 998 and 999) and two sites in the eastern equatorial Pacific (Sites 846 and 1241). The total range for ϵNd values measured from 18 to 4.5 Ma in the Caribbean is −7.3 to 0. These values are higher than Atlantic water masses (~–11) and range up to values equivalent to contemporaneous Pacific water masses, confirming that flow into the Caribbean Basin was composed of a mixture of Pacific and Atlantic waters, with an upper limit of almost pure Pacific-sourced waters. Throughout the Caribbean record, particularly during the carbonate crash (10–12 Ma), low carbonate mass accumulation rates (MARs) correlate with more radiogenic ϵNd values, indicating increased flow of corrosive Pacific intermediate water into the Caribbean Basin during intervals of dissolution. This flow pattern agrees with results from general ocean circulation models designed to study the effect of the shoaling of the Central American Seaway. Low carbonate MARs and high ϵNd values also correlate with intervals of increased Northern Component Water production and, therefore, enhanced conveyor circulation, suggesting that the conveyor may respond to changes in circulation associated with shoaling of the Central American Seaway. Reduced Pacific throughflow related to shoaling of the seaway led to a gradual increase in carbonate preservation and more Atlantic-like ϵNd values following the carbonate crash.
Assembly line job sequencing principles

Assembly line job sequencing establishes the order in which jobs are processed by an assembly line. This research focuses on job sequencing methods for assembly lines with work stations that receive the same fixed job sequence, are coupled together so that there is no work-in-process storage, and are balanced so that jobs move continuously between them at a constant rate. Automobile assembly lines frequently have these characteristics. Simple analytical principles are derived that aid in evaluating trade-offs between different job sequencing objectives. Included are set-up cost objectives related to operations performed on every job but in different choices (e.g. automobile painting) and capacity utilization objectives related to operations not performed on every job (e.g. installing vinyl roofs). These principles provide the basis for a job sequencing method that can be applied either by hand or with the help of a simple sorting routine.
Synthesis of diazomethyl β-d-galactopyranosyl and β-d-glucopyranosyl ketones. Potential affinity-labeling reagents for carbohydrate-binding proteins

3,7-Anhydro-1-deoxy-1-diazo-D-glycero-L-manno-2-octulose (6a; diazomethyl beta-D-galactopyranosyl ketone) and 3,7-anhydro-1-deoxy-1-diazo-D-glycero-D-gulo-2-octulose (6b; diazomethyl beta-D-glucopyranosyl ketone) have been prepared. Readily available C-glycosyl compounds possessing the appropriate stereo-chemistry and hydroxyl-group protection, viz., per-O-acetyl-2,6-anhydroheptononitriles and per-O-acetyl-2,6-anhydroheptonamides, were employed as precursors to per-O-acetyl-2,6-anhydroheptonic acids. These key intermediates were then converted into mixed carboxylic-carbonic acid anhydrides, and these caused to react with diazomethane, to give the corresponding per-O-acetyl-3,7-anhydro-1-deoxy-1-diazo-2-octuloses. Zemplen deacetylation gave, stereospecifically, the crystalline target-molecules in good overall yield. It is proposed that such C-glycosyl compounds as 6a and 6b, which possess the diazoacetyl functional groups as their "aglycon", will be useful as enzyme-activated irreversible inhibitors (suicide substrates) of glycosidases, and as photoaffinity-labeling reagents and classical affinity-labeling reagents for carbohydrate-binding proteins.
Diastereoselective Ni-catalyzed Negishi cross-coupling approach to saturated, fully oxygenated C-alkyl and C-aryl glycosides

A Ni-catalyzed Negishi cross-coupling approach to C-glycosides is described with an emphasis on C-aryl glycosides. The combination of NiCl2/PyBox in N,N'-dimethylimidazolidinone (DMI) enabled the synthesis of C-alkyl glycosides under mild reaction conditions. Moderate yields and beta-selectivities were obtained for C-glucosides, and good yields and high alpha-selectivities were the norm for C-mannosides. For C-aryl glycosides, reactions employing Ni(COD)2/(t)Bu-Terpy in N,N-dimethylformamide (DMF) were typically high yielding and provided C-glucosides with high beta-selectivities (1:>10 alpha:beta) and C-mannosides in moderate alpha-selectivities (3:1 alpha:beta); alpha-C-aryl glycosides could be obtained by the combination of Ni(COD)2/PyBox in DMF (>20:1 alpha:beta). The collective studies suggest that stereochemical control of the C-glycosides is dependent on the substrate and catalysts combination. The Negishi protocol displays excellent functional group tolerance, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.
Experimental study of robustness in adaptive control for large flexible structures

An experimental study is performed to investigate the robustness of model reference adaptive control for the large flexible structures control application. The main nonidealities of concern are unmodeled dynamics, input saturation, and time-delay effects (here, actuator and sensor dynamics are lumped into the last item for convenience). This study focuses on the robustness with respect to input saturation and time-delay effects, since robustness to unmodeled dynamics is inherent to the basic algorithm and has been demonstrated experimentally elsewhere. N experimental study is performed to investigate the robustness of model reference adaptive control for the large flexible structures control application. Although adaptive control methods are robust to parametric uncertainty by design, other types of nonidealities are known to lead to degradation and even instability of the closed-loop adaptive system. The main nonidealities of concern in the flexible structures control application are unmodeled dynamics, input saturation, and time-delay effects (here, actuator and sensor dynamics are lumped into the last item for convenience). Because of the use of the command generator tracker (CGT) approach, the adaptive algorithm considered here achieves tracking objectives that are in theory robust to unmodeled dynamics.1'2 This theoretical robustness to unmodeled dynamics has also been verified experimentally in Refs. 3 and 4 and will not be an issue in the present study. In contrast, there are presently no assurances as to the stability of the adaptive system to input saturation and time-delay effects. These latter issues will be the focus of the present study. It is shown experimentally in this paper that the basic adaptive algorithm is robust to input saturation, whereas timedelay effects can cause significant degradation and even instability. It is also shown experimentally that stability in the presence of time delay can be recovered by using a technique advocated by Bar-Kana5 of placing a small feedforward on the plant (or equivalently for the regulation problem, of placing a small feedback on the compensator). This stabilizes the closedloop system and recovers a certain degree of performance in the process. As a side benefit, the input torque requirements are also reduced. Certain theoretical results are included in this paper to support the experimental effort. In particular, it is shown that for structures with collocated actuators and sensors, there always exists a bounded feedforward gain that guarantees L2 stability of the closed-loop adaptive system in the presence of a pure time delay.
High Gain Micro-Channel Plate Multipliers for Particle Tracking or Single Photo-Electron Counting

Micro-channel plate multipliers have been used to detect the passage of relativistic charged particles. Measurements of the detection efficiency and pulse height response versus micro-channel plate gain are presented for one, two and three micro-channel plate arrays. Values describing temporal response and transit time jitter are also given. In a separate measurement, the response of a single micro-channel plate to individual slow electrons (< 1 keV) was studied. By using a special technique output bunches as small as three electrons may be seen for low average micro-channel plate gain. The results of attempts to improve the micro-channel plate response are also presented.
Effects of plasticity on convection in an ice shell: Implications for Europa

Abstract Europa's surface exhibits numerous pits, uplifts, and disrupted chaos terrains that have been suggested to result from convection in the ice shell. To test this hypothesis, we present numerical simulations of convection in an ice shell including the effects of plasticity, which provides a simple continuum representation for brittle or semibrittle deformation along discrete fractures. Plastic deformation occurs when stresses reach a specified yield stress; at lower stresses, the fluid flow follows a Newtonian, temperature-dependent viscosity. Four distinct modes of behavior can occur. For yield stresses exceeding ∼1 bar, plastic effects are negligible and stagnant-lid convection, with no surface motion and minimal topography, results. At intermediate yield stresses, a stagnant lid forms but deforms plastically, leading to surface velocities up to several millimeters per year. Slightly smaller yield stresses allow episodic, catastrophic overturns of the upper conductive lid, with (transient) stagnant lids forming in between overturn events. The smallest yield stresses allow continual recycling of the upper lid, with simultaneous, gradual ascent of warm ice to the surface and descent of cold, near-surface ice into the interior. The exact yield stresses over which each regime occurs depend on the ice-shell thickness, melting-temperature viscosity, and activation energy for viscous creep. To form hummocky matrix and translate chaos plates by several kilometers, substantial surface strain must accompany chaos formation, and the three plasticity-dominated convection modes described here can provide such deformation. Our simulations suggest that, if yield stresses of ∼0.2–1 bar are relevant to Europa, then convection in Europa's ice shell can produce chaos-like structures at the surface. However, our simulations have difficulty explaining Europa's numerous pits and uplifts. When plasticity forces the upper lid to participate in the convection, dynamic topography of ∼50–100-m amplitude results, but the topographic structures generally have diameters of 30–100 km, an order of magnitude wider than typical pits and uplifts. None of our simulations produced isolated pits or uplifts of any diameter.
Actions of certain arithmetic groups on Gromov hyperbolic spaces

Many interesting groups can be fruitfully studied via some natural action on a Gromov hyperbolic space. Examples include the action of an amalgam or HNN extension on its Bass–Serre tree, the action of a Kleinian group on H and the action of the mapping class group of a surface on the curve complex of that same surface. Alternatively, one can study the space of actions of a fixed group on some (fixed or varying) Gromov hyperbolic metric space. For example, the PSL.2;C/–character variety of a group parameterizes the space of actions of a fixed group on the hyperbolic space H . Analysis of the structure of this variety has led to many remarkable theorems about 3–manifolds and their fundamental groups (for an introduction, see Shalen [25]). A larger “variety” (in scare quotes because there is unlikely to be any algebraic structure) would describe all nontrivial actions on Gromov hyperbolic spaces, up to some appropriate equivalence relation. We give suggestions for how to define this equivalence relation and topologize the variety in Section 3. Briefly, the equivalence relation is that generated by coarsely equivariant quasi-isometric embeddings. This equivalence is coarser than that given by quasi-conjugacy (as in for instance Mosher, Sageev and Whyte [23]), but finer than that given by equivariant homeomorphism of limit sets. In this paper we concentrate on cases in which the set of equivalence classes is particularly simple.
CAT(0) spaces with polynomial divergence of geodesics

We construct a family of finite 2-complexes whose universal covers are CAT(0) and have polynomial divergence of desired degree. This answers a question of Gersten, namely whether such CAT(0) complexes exist.
Calculation of the Positronium Hyperfine Interval

We have completed the calculation of the one-photon-annihilation contribution to the positronium hyperfine interval at order $m{\ensuremath{\alpha}}^{6}$. Our result for this contribution is $\ensuremath{-}0.1256481(12)m{\ensuremath{\alpha}}^{6}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}2.344\mathrm{MHz}$. The complete theoretical result for this interval is worked out, and comparison with experiment is discussed.
Prospects of polarized fixed target Drell-Yan experiments

It has been proposed that the Siverse transverse single spin asymmetry in Drell-Yan production in transversely polarized p+p collisions would have an opposite sign compared to what has been observed in the polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) experiments. Experimental confirmation or disproval of this prediction would provide a novel fundamental test of QCD and shed new light on our theoretical understanding of the transverse spin physics phenomena. We discuss the prospects and physics sensitivities of polarized fixed target Drell-Yan experiments that could utilize the existing proton and other hadron beams at Fermilab, and polarized proton beams at RHIC with a polarized solid proton and/or neutron target option. We show that if realized, the new experiments would provide critical measurements of not only the sign change (or not) of Sivers functions, but also the information of quark and antiquark's Sivers distributions over a wide kinematic range.
A model for predicting pancreatic leakage after pancreaticoduodenectomy based on the international study group of pancreatic surgery classification

Backgrounds/aims With recent advances in pancreatic surgery, pancreaticoduodenectomy (PD) has become increasingly safe. However, pancreatic leakage is still one of the leading postoperative complications. An accurate prediction model for pancreatic leakage after PD can be helpful for pancreas surgeons. The aim of this study was to provide a new model that was simple and useful with high accuracy for predicting pancreatic leakage after PD. Methods To predict the occurrence of pancreatic leakage, several factors were selected using bivariate analysis and univariate logistic regression analysis. The final model was developed using multivariable logistic regression analysis in the model construction data set. Results Overall, 41 of 100 patients had pancreatic leakage by the International Study Group on Pancreatic Fistula (ISGPF) criteria. Soft pancreatic parenchyma, small pancreatic duct diameter (≤3 mm), and combined resection of SMV and portal vein were independently predictive of pancreatic leakage. The risk score (R) for individual patients can be calculated by combining the 3 prognostic values with the regression test: R=0.5986+(0.5533×pancreatic parenchyma)+(0.5448×pancreatic duct diameter)+(0.8453×combined resection). The overall predictive accuracy of the model, as measured by the receiver operating characteristic (ROC) curve, was 0.728. Conclusions Although continued refinements and improvements in the model are needed, the present model may assist pancreatic surgeons in the prediction of pancreatic leakage after PD.
Discrete Nonlinear Observers for Inertial Navigation

We derive an exact deterministic nonlinear observer to compute the continuous state of an inertial navigation system based on partial discrete measurements, the so-called strap-down problem. Nonlinear contraction is used as the main analysis tool, and the hierarchical structure of the system physics is systematically exploited. The paper also discusses the use of nonlinear measurements, such as distances to time-varying reference points.
Energetics of overall metabolic reactions of thermophilic and hyperthermophilic Archaea and Bacteria

Thermophilic and hyperthermophilic Archaea and Bacteria have been isolated from marine hydrothermal systems, heated sediments, continental solfataras, hot springs, water heaters, and industrial waste. They catalyze a tremendous array of widely varying metabolic processes. As determined in the laboratory, electron donors in thermophilic and hyperthermophilic microbial redox reactions include H2, Fe(2+), H2S, S, S2O3(2-), S4O6(2-), sulfide minerals, CH4, various mono-, di-, and hydroxy-carboxylic acids, alcohols, amino acids, and complex organic substrates; electron acceptors include O2, Fe(3+), CO2, CO, NO3(-), NO2(-), NO, N2O, SO4(2-), SO3(2-), S2O3(2-), and S. Although many assimilatory and dissimilatory metabolic reactions have been identified for these groups of microorganisms, little attention has been paid to the energetics of these reactions. In this review, standard molal Gibbs free energies (DeltaGr(0)) as a function of temperature to 200 degrees C are tabulated for 370 organic and inorganic redox, disproportionation, dissociation, hydrolysis, and solubility reactions directly or indirectly involved in microbial metabolism. To calculate values of DeltaGr(0) for these and countless other reactions, the apparent standard molal Gibbs free energies of formation (DeltaG(0)) at temperatures to 200 degrees C are given for 307 solids, liquids, gases, and aqueous solutes. It is shown that values of DeltaGr(0) for many microbially mediated reactions are highly temperature dependent, and that adopting values determined at 25 degrees C for systems at elevated temperatures introduces significant and unnecessary errors. The metabolic processes considered here involve compounds that belong to the following chemical systems: H-O, H-O-N, H-O-S, H-O-N-S, H-O-C(inorganic), H-O-C, H-O-N-C, H-O-S-C, H-O-N-S-C(amino acids), H-O-S-C-metals/minerals, and H-O-P. For four metabolic reactions of particular interest in thermophily and hyperthermophily (knallgas reaction, anaerobic sulfur and nitrate reduction, and autotrophic methanogenesis), values of the overall Gibbs free energy (DeltaGr) as a function of temperature are calculated for a wide range of chemical compositions likely to be present in near-surface and deep hydrothermal and geothermal systems.
Local and global Casimir energies for a semitransparent cylindrical shell

The local Casimir energy density and the global Casimir energy for a massless scalar field associated with a λδ-function potential in a (3 + 1)-dimensional circular cylindrical geometry are considered. The global energy is examined for both weak and strong coupling, the latter being the well-studied Dirichlet cylinder case. For weak coupling, through , the total energy is shown to vanish by both analytic and numerical arguments, based both on Green's-function and zeta-function techniques. Divergences occurring in the calculation are shown to be absorbable by renormalization of physical parameters of the model. The global energy may be obtained by integrating the local energy density only when the latter is supplemented by an energy term residing precisely on the surface of the cylinder. The latter is identified as the integrated local energy density of the cylindrical shell when the latter is physically expanded to have finite thickness. Inside and outside the δ-function shell, the local energy density diverges as the surface of the shell is approached; the divergence is weakest when the conformal stress tensor is used to define the energy density. A real global divergence first occurs in , as anticipated, but the proof is supplied here for the first time; this divergence is entirely associated with the surface energy and does not reflect divergences in the local energy density as the surface is approached.
Transonic region of high dynamic response encountered on an elastic supercritical wing

Unsteady aerodynamic data were measured on a 10.3 aspect-ratio elastic supercritical wing while undergoing high dynamic response above a Mach number of 0.90. These tests were conducted in the NASA Langley Transonic Dynamics Tunnel. A previous test of this wing predicted an unusual instability boundary based upon subcritical response data. During the present test, no instability was found, but an angle-of-attack dependent narrow Mach number region of high dynamic wing response was observed over a wide range of dynamic pressures. The effect on dynamic wing response of wing angle of attack, static outboard control surface deflection and a lower surface spanwise fence located near the 60% local chordline was investigated. The driving mechanism of the dynamic wing response appears to be related to chordwise shock movement in conjunction with flow separation and reattachment on both the upper and lower surfaces.
A nonspatial methodology for the analysis of two-way proximity data incorporating the distance-density hypothesis

This paper presents a nonspatial operationalization of the Krumhansl (1978, 1982) distancedensity model of similarity. This model assumes that the similarity between two objectsi andj is a function of both the interpoint distance betweeni andj and the density of other stimulus points in the regions surroundingi andj. We review this conceptual model and associated empirical evidence for such a specification. A nonspatial, tree-fitting methodology is described which is sufficiently flexible to fit a number of competing hypotheses of similarity formation. A sequential, unconstrained minimization algorithm is technically presented together with various program options. Three applications are provided which demonstrate the flexibility of the methodology. Finally, extensions to spatial models, three-way analyses, and hybrid models are discussed.
Chromium(0) promoted [6π+2π] cycloaddition reactions

Abstract The chromium(0) mediated [6+2] cycloaddition reactions of a variety of cyclic trienes with substituted alkenes is detailed. The reactions can be effected either photochemically or thermally. Reactions promoted with catalytic quantities of chromium(0) are also described.
Identification, Inference, and Sensitivity Analysis for Causal Mediation Effects

Causal mediation analysis is routinely conducted by applied researchers in a variety of disciplines. The goal of such an analysis is to investigate alternative causal mechanisms by examining the roles of intermediate variables that lie in the causal paths between the treat- ment and outcome variables. In this paper we first prove that under a particular version of sequential ignorability assumption, the aver- age causal mediation effect (ACME) is nonparametrically identified. We compare our identification assumption with those proposed in the literature. Some practical implications of our identification result are also discussed. In particular, the popular estimator based on the linear structural equation model (LSEM) can be interpreted as an ACME estimator once additional parametric assumptions are made. We show that these assumptions can easily be relaxed within and outside of the LSEM framework and propose simple nonparametric estimation strate- gies. Second, and perhaps most importantly, we propose a new sensi- tivity analysis that can be easily implemented by applied researchers within the LSEM framework. Like the existing identifying assumptions, the proposed sequential ignorability assumption may be too strong in many applied settings. Thus, sensitivity analysis is essential in order to examine the robustness of empirical findings to the possible existence of an unmeasured confounder. Finally, we apply the proposed methods to a randomized experiment from political psychology. We also make easy-to-use software available to implement the proposed methods.
Constraints on Eavesdropping on the BB84 Protocol

An undetected eavesdropping attack must produce count rate statistics that are indistinguishable from those that would arise in the absence of such an attack. In principle this constraint should force a reduction in the amount of information available to the eavesdropper. In this paper we illustrate, by considering a particular class of eavesdropping attacks, how the general analysis of this problem may proceed.
Detection of "Oncometabolite" 2-hydroxyglutarate by Magnetic Resonance Analysis as a Biomarker of IDH1/2 Mutations in Glioma

Somatic mutations in isocitrate dehydrogenase (IDH)1 and 2 have been identified in a subset of gliomas, rendering these tumors with elevated levels of “oncometabolite,” D-2-hydroxyglutarate (2HG). Herein, we report that 2HG can be precisely detected by magnetic resonance (MR) in human glioma specimens and used as a reliable biomarker to identify this subset of tumors. Specifically, we developed a two-dimensional correlation spectroscopy resonance method to reveal the distinctive cross-peak pattern of 2HG in the complex metabolite nuclear MR spectra of brain tumor tissues. This study demonstrates the feasibility, specificity, and selectivity of using MR detection and quantification of 2HG for the diagnosis and classification of IDH1/2 mutation-positive brain tumors. It further opens up the possibility of developing analogous non-invasive MR-based imaging and spectroscopy studies directly in humans in the neuro-oncology clinic.
ω-Iodoalkyl(methyl)malonate Esters

Abstract ω-Iodoalkyl(methyl)malonate esters have potential utility in the bioconjugate chemistry of steroids. A representative set of these esters with a variety of protecting groups and alkyl groups has been prepared. The compounds offer a range of elution values on silica, as well as several convenient deprotection options. ω-Bromoalkyl(methyl)malonate esters are precursors of chalcogenobarbiturates, which, in radiolabeled form, may be useful as brain imaging agents.[1] Recently, we have become interested in the analogous ω-iodoalkyl(methyl)malonate esters because of their possible utility in the bioconjugate chemistry of steroids. It is known that steroids can be conjugated to platinum through a malonate moiety.[2] Such platinated steroids are significant because of their potential as tissue-selective antitumor agents.
Development of side branching in dendritic crystal growth.

The growth of dendritic crystals of ${\mathrm{NH}}_{4}$Br from supersaturated solution has been studied in a way that allows high-resolution measurements of the early stages of side branching. The branches are found to be nonperiodic at any distance from the tip, with apparently random variations in both phase and amplitude. Side branches on opposite sides of the dendrite are imperfectly correlated. The rms side-branch amplitude is an exponential function of distance from the tip, with no apparent onset. The implications of these results for several theories of the stability of growing dendrites are discussed.
A Convenient Synthesis of Symmetric 1,2-Diarylethenes from Arylmethyl Phosphonium Salts

Symmetric ethenyldithiophenes are important intermediates for synthesis of photochromic materials and organic conductors. When acetonitrile is used as a solvent, 3-methylthiophenylphosphonium salts form symmetric ethenyldithiophenes in the presence of a strong base (e.g., NaH, tBuOK) in moderate to high yields. This homocoupling reaction is faster than a Wittig reaction with aromatic ketones in acetonitrile. Our study shows that the presence of polar aprotic solvents promotes the homocoupling reaction.
Bounds on the size of test sets for sorting and related networks

Abstract We study the size of the smallest test set to decide if a network is a sorting network (sorter), i.e. if it can sort all inputs. Our results include: (i) The size of the smallest test set to test if a network with n inputs is a sorter is exactly (2 n − n − 1) if 0, 1-inputs are used and exactly ( ⌊n 2⌋ n )−1 if permutations of (1 2 3 ⋯ n ) are used as inputs. (ii) The size of the smallest test set to test if a network is a ( k , n )-selector is exactly Σ k j=0 ( n j ) − k − 1 for 0, 1 inputs and ( min{ ⌊n 2⌋ n ,k} ) − 1 for permutation inputs. (iii) The size of the smallest test set to test if a network is a merging network is exactly n 2 /4 if 0, 1 inputs are used and exactly n /2 for permutation inputs.
Terminal ion source for an FN tandem

Abstract An RF discharge source assembly has been developed for use in the terminal of the FN tandem Van de Graaff accelerator at the Nuclear Physics Laboratory of the University of Washington. The primary motivation for developing the source was to provide a high intensity beam of 3 H + to produce 8 B from the reaction 6 Li( 3 He,n) 8 B. The design of the optics and the performance of the source are described here.
Folding-induced CO2-soluble peptides

The first CO2- and water-soluble peptide is reported, in which folding facilitates its solubility in CO2.
Experimental Characterization of Aerodynamic Behavior of Membrane Wings in Low-Reynolds-Number Flow

An experimental study of the aerodynamic characteristics of a flat-plate membrane wing was conducted. Three different values of membrane prestrain (5, 7, and 10%) were investigated, along with a rigid flat plate, at Reynolds numbers of 13,700, 22,600 and 36,300 and angles of attack up to 27 deg. It was found that 1) the dependence of the prestall mean lift on model prestrain is negligible, 2) prestall mean lift at a given level of prestrain is a strong function of Reynolds number, and 3) the mean drag increased with a decrease in model prestrain. In addition, the stall angle of attack is weakly dependent on prestrain and increases with increasing Reynolds number. With the exception of the highest Reynolds number, the flexible-model stall angles were found to be similar to the rigid flat-plate results. At the largest Reynolds number, dynamic results for the flexible models revealed large rms values of lift and drag, which generally decrease with increasing angle of attack. In comparison to the flexible models, the rms values for the rigid flat plate were insignificant. An aeroelastic flutter instability is postulated to be the cause of the large dynamic response for the flexible models. This hypothesis is supported by results that were generated using a potential flow- based computational aeroelastic model. These aeroelastic instability-induced vibrations are also proposed as the mechanism by which the flexible models showed better stall characteristics at the highest-tested Reynolds number.
Conversion of Propargylic Alcohols to β-Oxo Esters Catalyzed by Novel Ruthenium-Phosphoramidite Complexes

A series of half-sandwich phosphoramidite complexes of ruthenium were synthesized and employed as catalysts in the atom-economical formation of β-oxo esters from carboxylic acids and propargylic alcohols. Reaction of the phosphoramidites (R)-BINOL-PNR 2 (R=Me, la; i-Pr, 1b; benzyl, 1c) and (rac)-6,6'-dibromo-BINOL-PNMe2 (1d) with the dimeric p-cymene-ruthenium dichloride complex, [RuCl 2 (p-cymene)] 2 , gave the complexes [RuCl 2 (p-cymene)(L)] (L=la, 7a; 1b, 7b; 1c, 7c; 1d, 7d) in 96-66% yield. Accordingly, reaction of (R)-BINOL(8H)-PNMe 2 (2a) and (R)-BINOL(8H)-PN-(benzyl) 2 (2b) with [Rucl 2 (p-cymene)] 2 afforded the complexes [Rucl 2 (p-cymene)(L)] (L=2a, 8a; 2b, 8b) in 82% and 86% yield. In a similar reaction, treatment of (R)-BIPHEN-PNMe 2 (9) with [RuCl 2 (P-cymene)] 2 gave the complex [RuCl 2 (P-cymene)(9)] (11) in 60% yield. Finally, phosphoramidite 1b reacted with [Rucl 2 (C 6 Me 6 )] 2 to give [RuCl 2 (C 6 Me 6 )(1b)] (12) in 78% yield. All novel complexes are catalytically active in the formation of β-oxo esters from propargylic alcohols and carboxylic acids. Standard conditions involve cyclohexane solvent, propargylic alcohol (1.0 equiv.), carboxylic acid (1.0 equiv.), ruthenium catalyst (1.5 mol%), and 90°C for 5-18 h. Isolated yields of the β-oxo esters range from 87 to 16% and show broad substrate generality. The reaction proceeds without racemization if a chiral propargylic alcohol is employed. The method is practical as no additives are required and the exclusion of oxygen and moisture is not needed. Complex 7c turned out to be the most effective catalyst (5 h reaction time), showing that the ligand structure has a profound impact on the catalytic performance. The crystal structure of 7a was determined, confirming an octahedral coordination geometry about the ruthenium center.
Employing the one-sender-multiple-receiver technique in wireless LANs

In this paper, we study the One-Sender-Multiple-Receiver (OSMR) transmission technique, which allows one sender to send to multiple receivers simultaneously by utilizing multiple antennas at the sender. To study the physical-layer characteristics of OSMR, we implement a prototype OSMR transmitter/receiver with GNU software defined radio and conduct experiments in a university building. Our results are positive and show that wireless channels allow OSMR for a significant percentage of the time. Motivated by our physical-layer study, we propose extensions to the 802.11 MAC protocol to support OSMR transmission, which is backward-compatible with existing 802.11 devices. We also note that the access point (AP) needs a packet scheduling algorithm to efficiently exploit OSMR. We show that the scheduling problem without considering the packet transmission overhead can be formalized as a linear programming problem, but the scheduling problem considering the overhead is NP-hard. We then propose a practical scheduler based on a two-phase algorithm that can also handle channel fluctuations. We test the proposed protocol and algorithm with simulations driven by traffic traces collected from wireless LANs and channel-state traces collected from our experiments, and the results show that OSMR significantly improves the downlink performance.
The General Motors' variation‐reduction adviser: an example of grassroots knowledge management development

One approach to developing knowledge management systems is to seed the system in key communities of practice and then encourage its customization and spread throughout the enterprise by local (‘grassroots’) initiative. This has the beneﬁt of worker buy-in and adaptation of the local systems to their workﬂows. The concept is that, in exchange for some loss of control and standardization, the grassroots systems will be used and appreciated and will grow into an enterprise-wide system. In this paper, we discuss this approach and how it is emerging in General Motors' Variation-Reduction Adviser, a manufacturing knowledgesharing and lessons-learned system. Copyright © 2003 John Wiley & Sons, Ltd.
Three-candidate competition when candidates have valence: the base case

We study the Nash Equilibrium of three-candidate unidimensional spatial competition when candidates differ in their non-policy characteristics (valence). If the voters’ policy preferences are represented by a strictly convex loss function, and if the voter density is unimodal and symmetric, then a unique, modulo symmetry, Local Nash Equilibrium exists under fairly plausible conditions. The global Nash Equilibrium, however, exists when only one candidate has a valence advantage (or disadvantage) while the other two candidates have the same valence.
L-functions with large analytic rank and abelian varieties with large algebraic rank over function fields

The goal of this paper is to explain how a simple but apparently new fact of linear algebra together with the cohomological interpretation of L-functions allows one to produce many examples of L-functions over function fields vanishing to high order at the center point of their functional equation. Conjectures of Birch and Swinnerton-Dyer, Bloch, and Beilinson relate the orders of vanishing of some of these L-functions to Mordell-Weil groups and other groups of algebraic cycles. For certain abelian varieties of high analytic rank, we are also able to prove the conjecture of Birch and Swinnerton-Dyer thus establishing the existence of large Mordell-Weil groups in those cases. In the rest of this section we state the main results of the paper.
Adaptive detection and enhancement of multiple sinusoids using a cascade IIR filter

A constrained adaptive infinite-impulse-response (IIR) filter consisting of a cascade of biquadratic notch sections is used to track multiple sinusoids. The structure can be used to isolate individual sinusoids. It is shown that for small changes around the optimum solution, the proposed update algorithm approximates the Gauss-Newton update without requiring a matrix inversion. Furthermore, the transient response is approximately independent of the number of sinusoids or their power levels. Important adaptive line enhancement performance criteria, such as signal-to-noise improvement ratio and the bias in the frequency estimate assuming white noise, are derived for the single-sinusoid case. Computer simulations are used to demonstrate the performance of the notch filter under a wide range of conditions. >
The energy of C4-free graphs of bounded degree

Abstract Answering some questions of Gutman, we show that, except for four specific trees, every connected graph G of order n , with no cycle of order 4 and with maximum degree at most 3, satisfies ∣ μ 1 ∣ + ⋯ + ∣ μ n ∣ ⩾ n , where μ 1 , … , μ n are the eigenvalues of G . We give some general results and state two conjectures.
Temperature minimum heating in solar flares by resistive dissipation of Alfven waves

The possibility that the strong heating produced at temperature-minimum levels during solar flares is due to resistive dissipation of Alfven waves generated by the primary energy release process in the corona is studied. It is shown how, for suitable parameters, these waves can carry their energy essentially undamped into the temperature-minimum layers and can then produce a degree of heating consistent with observations.
Schooling and economic growth: A King–Rebelo experiment with human capital ☆

Abstract Education is added to the standard Neoclassical growth model by calibrating a human capital technology to the empirical evidence on schooling. Simulation experiments patterned after King and Rebelo (1993. American Economic Review 83, 908–931) are conducted. When agents act as if they are infinitely lived, interest rates are too high and the rise in school spending is too weak over the transitional growth path. When schooling is inefficiently low due to binding intergenerational credit constraints, interest rates deviate only moderately from the steady-state level and the historical rise in school spending is fully explained.
Scaling behavior of the four-point renormalized coupling constant in the two dimensional O(2) and O(3) non-linear sigma models

Abstract We report thermodynamic values of four-point renormalized coupling constant calculated by Monte Carlo simulations in the continuum limits of the lattice versions of the two-dimensional O(2) and O(3) non-linear sigma models. In each case the critical index of the coupling constant vanishes, which leads to hyperscaling (non-triviality).
Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS 2397a

Using the adaptive optics system, Hokupa`a, at Gemini North, we have directly imaged a companion around the UKIRT faint standard M8 star LHS 2397a (FS 129) at a separation of 2.96 AU. Near-infrared photometry of the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be M8. We also derive a substellar mass of the companion of 0.068 M☉, although masses in the range 0.061-0.069 M☉ are possible, and the primary mass is 0.090 M☉ (0.089-0.094 M☉). Reanalysis of archival imaging from the Hubble Space Telescope has confirmed the secondary as a common proper motion object. This binary represents the first clear example of a brown dwarf companion within 4 AU of a low-mass star and should be one of the first late-L dwarfs to have a dynamical mass. As part of a larger survey of M8-L0 stars, this object may indicate that there is no "brown dwarf desert" around low-mass primaries.
Left Ventricular Dysfunction in Chronic Constrictive Pericarditis

Left ventricular function was assessed in six patients with chronic constrictive pericarditis by means of biplane 35 mm cineangiography performed at 60 frames per second. A significant reduction below normal was noted for several values, including end-diastolic volume, stroke index, ejection fraction, total circumferential fiber shortening, and percent shortening. In addition, the maximal observed rate of circumferential fiber shortening was reduced from an average normal value of 31.64 cm/sec to 21.04. When the maximal observed rate of circumferential fiber shortening was plotted against wall tension, it was noted that for any level of wall tension the maximal rate of fiber shortening was reduced in the subjects with chronic constrictive pericarditis. Pressure-volume loops were narrowed and shifted upward and to the left. Thus, the directional changes in volume, circumferential fiber shortening and tension-velocity relations suggest left ventricular dysfunction in patients with chronic constrictive pericarditis.
Tidal Evolution by elongated primaries: Implications for the Ida/Dactyl System

The age of asteroid 243 Ida's satellite Dactyl is < 100 myr according to the conventional formula for the rate of tidal evolution outward from Ida, contrary to estimates based on the likely age of the asteroid itself (∼ 1 byr). We investigate whether this discrepancy may be due to the conventional formula for tidal evolution being based on a spherical primary, whereas Ida is actually highly elongated. A model for Ida consisting of three spheres connected by damped springs is used to estimate what effects the elongation may have on the tidal dissipation. In fact, our model gives torques and energy dissipation similar to that in an equivalent sphere, indicating that the spherical model gives reasonable results even when applied to an elongated or irregular body.
Heegaard surfaces for certain graphs in compressionbodies

Let M be a compressionbody containing a properly embedded graph T (with at least one edge) such that ∂+M−T is parallel to the frontier of T∪∂−M in M. We extend methods of Hayashi and Shimokawa to show that if H is a bridge surface for T then one of the following occurs: H is stabilized, boundary stabilized, or perturbed. T contains a removable path. M is a trivial compressionbody and H−T is properly isotopic in M−T to ∂+M−T.
A multiparameter analysis of the boundedness problem for vector addition systems

Abstract Let VASS(k, l, n) denote the class of k-dimensional n-state Vector Addition Systems with States, where the largest integer mentioned, in an instance, can be represented in l bits. Using a modification of the technique used by C. Rackoff (Theoret. Comput. Sci.6 (1978), 223–231) we show that the Boundedness Problem (BP), for VASS(k, l, n), can be solved in O((l + log n) ∗ 2 c ∗ k ∗ log k ) nondeterministic space. By modifying R. Lipton's (“The Reachability Problem Requires Exponential Space,” Report No. 62, Department of Computer Sciences, Yale University, Jan. 1976) result, a lower bound is then shown of O((l + log n) ∗ 2 c ∗ k ) non-deterministic space. Thus, the upper bound is optimal with respect to parameters l and n, and is nearly optimal with respect to the parameter k. This yields an improvement over the result of Rackoff, especially when compared with the lower bound of Lipton. This is because the lower bound, of O(2 c ∗ k ) space, was essentially given for VASS(k, 1, 1). Now Rackoff's corresponding upper bound, just for the instances of VASS(k, 1, 1) constructed by Lipton, is no better than O(2 c ∗ k 2 log k ) space. (In general, it can get much worse.) Our result, however, yields an upper bound of O(2 c ∗ k ∗ log k ) , over the entire class. We also investigate the complexity of this problem for small, but fixed, values of k. We show that the BP is PSPACE-complete for four-dimensional VASSs, and NP-hard for two-dimensional VASSs. The above results can then be extended for the case without states. In particular, we are able to show that the BP is NP-hard for VASS(3, l, 1) and PSPACE-complete for VASS(4, l, 1). Extensions to related problems (e.g., covering and reachability) are also discussed.
QCD hadron spectrum with domain wall fermions

Abstract We present the QCD hadron spectrum for the cases of both quenched and two-flavor dynamical domain wall fermions. We compare the results obtained using the Wilson gauge action and a renormalization group improved gauge action. Finite volume effects and the dependence on the finite extent of the fifth dimension are discussed.