cssi/SciSciGPT-SciSciNet huggingface dataset:
Chattering problem in sliding mode control systems

Abstract In practical applications of sliding mode control, engineers may experience undesirable phenomenon of oscillations having finite frequency and amplitude, which is known as ‘chattering'. At the first stage of sliding mode control theory development the chattering was the main obstacle for its implementation. Chattering is a harmful phenomenon because it leads to low control accuracy, high wear of moving mechanical parts, and high heat losses in power circuits. There are two reasons which can lead to chattering. The chattering can be caused by fast dynamics which were neglected in the ideal model. These ‘unmodeled’ dynamics with small time constants are usually disregarded in models of servomechanisms, sensors and data processors. The second reason of chattering is utilization of digital controllers with finite sampling rate, which causes so called ‘discretization chatter'. Theoretically the ideal sliding mode implies infinite switching frequency. Since the control is constant within a sampling interval, switching frequency can not exceed that of sampling, which lead to chattering as well. Mechanism of chattering generating is demonstrated for control of inverted an pendulum with unmodeled actuator dynamics. The efficient recipe for chattering suppression is use of asymptotic observers. The main idea of using an asymptotic observer to prevent chattering is to generate ideal sliding mode in the auxiliary loop including the observer. In the observer loop, sliding mode is generated in the control software; therefore, any unmodeled dynamics which cause chattering can be excluded. As follows from analysis, based on the describing function method, the amplitude of chattering is proportional to magnitude of discontinuous control. Therefore the methods of chattering suppression can be developed such that the magnitude is decreased properly holding the establishment of sliding mode. First option is to decrease the magnitude along with the system states. The second one implies that the magnitude is the function of an equivalent control derived by a low-pass filter ueq. The method can be applied for the plants subjected to unknown disturbances. “Discretization chattering” in discrete-time systems is caused by discontinuities in control. Increasing a sampling frequency to decrease the chattering amplitude seems unjustified, since using a computer is adequate to control system dynamics if a sampling frequency corresponds to average, slow system motion rather than to a high frequency component. First the definition of sliding mode is introduced embracing both discrete- and continuous-time systems. Then free of chattering design methodology is proposed for discrete-time systems. The fundamental difference is that the control should be a continuous function of the state. Experimental results for sliding mode control of inductions motors with observers are discussed.
Rainbow trapping in hyperbolic metamaterial waveguide

We propose a hyperbolic metamaterial waveguide to realize a highly efficient rainbow trapping effect, which can be used to develop practical on-chip optical super absorbers with a tunable absorption band.
Delayed intraocular pressure elevation after pupillary dilation in exfoliation syndrome.

. Purpose: To determine the effect of pupillary dilation on intraocular pressure (IOP) in normotensive patients with exfoliation syndrome (XFS). Methods: Patients with XFS were enrolled in this prospective trial. All eyes were untreated, had no previous laser or operative surgery and were normotensive with full visual fields and open angles. IOP was measured before dilation and hourly for four consecutive hours after dilation with tropicamide 1% and phenylephrine 2.5% eyedrops. Results: Twenty-five eyes of 19 White patients (nine male, 10 female) with XFS were enrolled. Twelve eyes (48%) had a rise in IOP of ≥ 4 mmHg above the pre-dilation baseline IOP and four (16%) had a rise of ≥ 9 mmHg (9–28 mmHg). Post-dilation gonioscopy confirmed the presence of an open anterior chamber angle in all eyes. The maximum IOP was reached 3 hr post-dilation in three eyes and after 2 hr in the remaining eyes. The four eyes with marked IOP rise exhibited an elevation of between 1 and 7 mmHg at 1 hr. Extensive pigment release was noticed in all eyes that had a rise in IOP. Conclusion: Patients with XFS are at risk of developing delayed post-dilation IOP rises. Awareness of this phenomenon is particularly important in patients with advanced cupping and/or severe visual field loss who may not be able to tolerate a marked elevation of IOP. An early, mild rise in IOP at 1 hr may serve as a warning sign for a more severe, delayed response. Eyes with XFS should be monitored carefully after dilation, especially those with marked pigment release.
Indentation modulus and hardness of whisker-reinforced heat-cured dental resin composites.

Abstract Objectives: Recent studies showed that ceramic whisker reinforcement imparted a two-fold increase in the strength of dental composites. The aim of this study was to investigate the indentation response and measure the elastic modulus, hardness, and brittleness of whisker-reinforced heat-cured resin composites as a function of filler level, heat-cure temperature, and heat-cure duration. Methods: Silica particles were fused onto silicon nitride whiskers to facilitate silanization and to roughen the whiskers for improved retention in matrix. Whisker filler mass fractions of 0, 20, 40, 60, 70, 74 and 79% were tested. Heat-cure temperature ranged from 100 to 180°C, and duration from 10 min to 24 h. A nano-indentation system enabled the measurement of elastic modulus. Fracture toughness was measured and composite brittleness index was calculated. An inlay/onlay composite and a prosthetic composite were tested as controls. Results: Whisker filler level and heat-cure duration had significant effects on composite properties, while heat-cure temperature had non-significant effects. The whisker composite with 79% filler level had a modulus in GPa (mean (SD); n=6) of 26.9 (1.0), significantly higher than 15.1 (0.2) of an inlay/onlay control, and 16.1 (0.3) of a prosthetic control (Tukey's multiple comparison test; family confidence coefficient=0.95). The fracture toughness in MPa·m1/2 was 2.22 (0.26) for the whisker composite, higher than 0.95 (0.11) for inlay/onlay control, and (1.13±0.19) for prosthetic control. The brittleness index was (0.49±0.07) for whisker composite, lower than (1.02±0.12) for inlay/onlay control and (0.63±0.13) for prosthetic control. Significance: Whisker filler level had a profound influence, heat-cure duration had significant effects, while temperature did not have significant effects, on the properties of whisker composite. The whisker composite had significantly higher elastic modulus and fracture toughness, and lower brittleness than the inlay/onlay and prosthetic controls.
Correction for restriction of range when both X and Y are truncated

The effect of range restriction on one variable in a bivariate normal distribution on the X-Y correlation and the problem of estimating unrestricted from re stricted correlations has been widely studied for more than half a century. The behavior of correction formu las under truncation of both X and Y, however, re mains largely unresearched. The performance of the correction formula for unidimensional truncation (Thorndike, 1947, Case 2) and an approximation pro cedure for correcting for bidimensional truncation pro posed by Wells and Fruchter (1970) were investigated. The Thorndike correction formula undercorrects in most circumstances. The Wells and Fruchter procedure performs quite well under most conditions but often results in a slight overcorrection. The performance of the Wells and Fruchter and Thorndike formulas are also compared under truncation on X or Y alone. In these circumstances the Wells and Fruchter correction is either equal or markedly superior to the traditional correction. Based on ov...
Detecting Gravitational Lensing Cosmic Shear from Samples of Several Galaxies Using Two-dimensional Spectral Imaging

Studies of weak gravitational lensing by large-scale structures require the measurement of the distortions introduced to the shapes of distant galaxies at the few percent level by anisotropic light deflection along the line of sight. In order to detect this signal on 1'-10' scales in a particular field, accurate measurements of correlations between the shapes of order 103-104 galaxies are required. This large-scale averaging is required to accommodate the unknown intrinsic shapes of the background galaxies, even with careful removal of systematic effects. Here an alternative is discussed. If it is possible to measure accurately the detailed dynamical structure of the background galaxies, in particular rotating disks, then it should be possible to measure directly the cosmic shear distortion since it generally leads to a non-self-consistent rotation curve. Narrow spectral lines and an excellent two-dimensional spatial resolution are required. The ideal lines are CO rotational transitions, and the ideal telescope is the Atacama Large Millimeter Array.
Precision Photometry for Q0957+561 Images A and B

Since the persuasive determination of the time delay in Q0957+561, much interest has centered around shifting and subtracting the A and B light curves to look for residuals due to microlensing. Solar mass objects in the lens galaxy produce variations on timescales of decades, with amplitudes of a few tenths of a magnitude, but MACHOs (with masses of order 10-3-10-7 M☉) produce variations at only the 5% level. To detect such small variations, highly precise photometry is required. To that end, we have used 150 observations over three nights to examine the effects of seeing on the light curves. We have determined that seeing itself can be responsible for correlated 5% variations in the light curves of A and B, which could masquerade as microlensing events. We have found, however, that these effects can be accurately removed by subtracting the light from the lens galaxy and by correcting for cross contamination of light between the closely juxtaposed A and B images. We find that these corrections improve the variations due to seeing from 5% to a level on the order of the photon shot noise (0.5%). We also find that this corrected aperture photometry method is more reliable at removing the errors due to seeing than is a direct implementation of point-spread function fitting photometry.
Origin of Tektites.

IN a recent communication1, Dr. Kohman suggests that tektites are meteorites which originate in interstellar space and collide with the solar system. I should like to direct attention again to the various facts that must be explained by any acceptable postulated history of these objects. (1) Tektites have chemical compositions remarkably similar to those of the more acid sedimentary rocks. This is true for the major and minor constituents. (I have been privileged to see analyses as yet unpublished on these minor constituents.) Such a chemical composition is not produced by any other naturally occurring chemical processes that we know of, except perhaps in very rare and special circumstances. (2) Tektites obviously have been melted, and this means that a temperature of some 1,500° C. or more was supplied by some means. In fact some appear to have been reheated to the melting point by passage through gas or by a blast of gas over the object. No terrestrial source of heat is known which could produce such high temperatures. (3) They are distributed thinly over areas of hundreds and thousands of kilometres in linear dimensions. (4) They are reported to contain aluminium-26 and beryllium-10. This observation is due to Dr. Kohman and Dr. Ehmann.
Highly practical copper(I)/TEMPO catalyst system for chemoselective aerobic oxidation of primary alcohols.

Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups.
Control of a variable ratio gearbox and mechanical brake to maximize wind energy production

The purpose of the authors' research is to develop a variable ratio gearbox (VRG) that enables discrete variable speed operation for fixed-speed wind turbines in the production range of 50 to 500 kW. Previous work suggests that this device can increase power production by 7% over the original configuration. The current study further increases the wind capture by applying control to the VRG and mechanical brake. In this technique the selected gear ratio produces torque slightly above the level that is required, by the generator, for full power. This excess torque is removed through the mechanical brake, and full load production is realized simultaneously. This paper discusses the framework and decision-making protocol used to control these two subsystems. The control design process uses dynamic programming to insure maximum energy production while conserving brake liner. System performance is simulated for twenty sets of wind data that cover a wide range of wind conditions. The results demonstrate that full production can be achieved across greater ranges of wind speed, and can increase electrical production by an average of 10% for the sites considered.
Implicit Turbulence Modeling for High Reynolds Number Flows

We continue our investigation of the implicit turbulence modeling property of the nonoscillatory finite volume scheme MPDATA. We start by comparing MPDATA simulations of decaying turbulence in a triply periodic cube with analogous pseudospectral studies. In the regime of direct numerical simulation, MPDATA is shown to agree closely with the pseudospectral model. As viscosity is reduced, the two model results diverge. We study the MPDATA results in the inviscid limit, using a combination of mathematical analysis and computational experiment. We validate the inviscid MPDATA results as representing the turbulent flow in the limit of very high Reynolds number.
An accuracy assessment of Cartesian-mesh approaches for the Euler equations

A critical assessment of the accuracy of Cartesian-mesh approaches for steady, transonic solutions of the Euler equations of gas dynamics is made. An exact solution of the Euler equations (Ringleb's flow) is used not only to infer the order of the truncation error of the Cartesian-mesh approaches, but also to compare the magnitude of the discrete error directly to that obtained with a structured mesh approach. Uniformly and adaptively refined solutions using a Cartesian-mesh approach are obtained and compared to each other and to uniformly refined structured mesh results. The effect of cell merging is investigated as well as the use of two different K-exact reconstruction procedures. The solution methodology of the schemes is explained and tabulated results are presented to compare the solution accuracies.
Achievable Rates for $K$ -User Gaussian Interference Channels

The aim of this paper is to study the achievable rates for a K-user Gaussian interference channel (G-IFC) for any signal-to-noise ratio using a combination of lattice and algebraic codes. Lattice codes are first used to transform the G-IFC into a discrete input--output noiseless channel, and subsequently algebraic codes are developed to achieve good rates over this new alphabet. In this context, a quantity called efficiency is introduced which reflects the effectiveness of the algebraic coding strategy. This paper first addresses the problem of finding high-efficiency algebraic codes. A combination of these codes with Construction-A lattices is then used to achieve nontrivial rates for the original G-IFC.
A Comparison of Higher-Order Difference Methods in the Solution of Beam-Vibration Problems

Several higher-order difference methods are investi gated and compared for the problem of finding the natural frequencies of the lateral vibration of a beam. All of the methods considered are applicable to either digital or analog computers, although particu lar reference is made to the analog computer.The methods considered in most detail use the same basic central difference approximation, the variations occurring in the method of representing boundary conditions. Three higher-order approaches to the problem of boundary conditions are pre sented. They are 1) the use of one-sided differences of fourth order, 2) the use of symmetry assumptions, and 3) the passive-circuit approach. Each method is shown to have its advantages, the final choice de pending upon the particular requirements of the problem.Results are presented in the form of curves of per centage mode-frequency error vs number of cells for the various approximation methods.
Coalescing systems of non-Brownian particles

A well-known result of Arratia shows that one can make rigorous the notion of starting an independent Brownian motion at every point of an arbitrary closed subset of the real line and then building a set-valued process by requiring particles to coalesce when they collide. Arratia noted that the value of this process will be almost surely a locally finite set at all positive times, and a finite set almost surely if the initial value is compact: the key to both of these facts is the observation that, because of the topology of the real line and the continuity of Brownian sample paths, at the time when two particles collide one or the other of them must have already collided with each particle that was initially between them. We investigate whether such instantaneous coalescence still occurs for coalescing systems of particles where either the state space of the individual particles is not locally homeomorphic to an interval or the sample paths of the individual particles are discontinuous. We give a quite general criterion for a coalescing system of particles on a compact state space to coalesce to a finite set at all positive times almost surely and show that there is almost sure instantaneous coalescence to a locally finite set for systems of Brownian motions on the Sierpinski gasket and stable processes on the real line with stable index greater than one.
Completely invariant sets of normality for rational semigroups

Let G be a semigroup of rational functions of degree at least two where the semigroup operation is composition of functions. We prove that the largest open subset of the Riemann sphere on which the semigroup G is normal and is completely invariant under each element of G, can have only 0,1,2, or infinitely many components.
Sensitivity of Neutrino Mass Experiments to the Cosmic Neutrino Background

The KATRIN neutrino experiment is a next-generation tritium beta decay experiment aimed at measuring the mass of the electron neutrino to better than 200 meV at 90% C.L. Because of its intense tritium source, KATRIN can also serve as a possible target for the process of neutrino capture, ${\ensuremath{\nu}}_{e}+^{3}\mathrm{H}\ensuremath{\rightarrow}^{3}\mathrm{He}^{+}+{e}^{\ensuremath{-}}$. The latter process, possessing no energy threshold, is sensitive to the cosmic neutrino background ($\mathrm{C}\ensuremath{\nu}\mathrm{B}$). In this paper, we explore the potential sensitivity of the KATRIN experiment to the relic neutrino density. The KATRIN experiment is sensitive to a $\mathrm{C}\ensuremath{\nu}\mathrm{B}$ overdensity ratio of $2.0\ifmmode\times\else\texttimes\fi{}{10}^{9}$ over standard concordance model predictions (at 90% C.L.), addressing the validity of certain speculative cosmological models.
An iterative scheme for solving nonlinear equations with monotone operators

An iterative scheme for solving ill-posed nonlinear operator equations with monotone operators is introduced and studied in this paper. A discrete version of the Dynamical Systems Method (DSM) algorithm for stable solution of ill-posed operator equations with monotone operators is proposed and its convergence is proved. A discrepancy principle is proposed and justified. A priori and a posteriori stopping rules for the iterative scheme are formulated and justified.
Use of remote sensing data for estimation of winter wheat yield in the United States

This paper shows the application of remote sensing data for estimating winter wheat yield in Kansas. An algorithm uses the Vegetation Health (VH) Indices (Vegetation Condition Index (VCI) and Temperature Condition Index (TCI)) computed for each week over a period of 23 years (1982-2004) from Advance Very High Resolution Radiometer (AVHRR) data. The weekly indices were correlated with the end of the season winter wheat (WW) yield. A strong correlation was found between winter wheat yield and VCI (characterizing moisture conditions) during the critical period of winter wheat development and productivity that occurs during April to May (weeks 16 to 23). Following the results of correlation analysis, the principal components regression (PCR) method was used to construct a model to predict yield as a function of the VCI computed for this period. The simulated results were compared with official agricultural statistics showing that the errors of the estimates of winter wheat yield are less than 8%. Remote sensing, therefore, is a valuable tool for estimating crop yields well in advance of harvest, and at a low cost.
Effects of antenna position on readability of RFID tags in a refrigerated sea container of frozen bread at 433 and 915 MHz

Abstract Perishable foods are frequently exposed to temperature abuse during transportation and distribution. The use of traditional data loggers do not permit the instantaneous data transmission that radio frequency technology offers. Temperature has a major impact on food quality and safety, particularly when long transit times are imposed. Consequently, using radio frequency identification (RFID) to track and monitor temperature in perishable shipments will bring significant benefits to the cold chain. The goal of this study was to determine the optimal RF antenna placement to achieve full RFID tag readability inside a sea container. Testing was made at two different frequencies (915 and 433 MHz) while the refrigeration unit was running at −25 °C and the container was fully loaded with frozen bread. The sea container was instrumented with eight RFID antennas, three of which were tuned for 433 MHz and five for 915 MHz. All antenna wires exited the container via the forward drain holes. The RFID readers were outside the container and connected to their respective antennas, one at a time. Thirty eight RFID tags were evenly distributed onto the pallets of frozen bread. All RFID tags were active tags capable of reading and recording temperature. Results at 915 MHz showed readability levels between 47% and 79%, with an average of 68.4%, whereas 433 MHz demonstrated 100% readability at all antenna positions. In conclusion, the 433 MHz RFID system appears suitable for real time temperature monitoring of frozen bread inside a sea container. This technology could be applied to other food items similar to frozen bread.
Isotropic loop quantum cosmology

Isotropic models in loop quantum cosmology allow explicit calculations, thanks largely to a completely known volume spectrum, which is exploited in order to write down the evolution equation in a discrete internal time. Because of genuinely quantum geometrical effects, the classical singularity is absent in those models in the sense that the evolution does not break down there, contrary to the classical situation where spacetime is inextendible. This effect is generic and does not depend on matter violating energy conditions, but it does depend on the factor ordering of the Hamiltonian constraint. Furthermore, it is shown that loop quantum cosmology reproduces standard quantum cosmology and hence (e.g., via WKB approximation) classical behaviour in the large volume regime where the discreteness of space is insignificant. Finally, an explicit solution to the Euclidean vacuum constraint is discussed which is the unique solution with semiclassical behaviour representing quantum Euclidean space.
The Chemistry of 1,2-Dithiins

Abstract This report describes the bioactivity, the chemistry, and the synthesis of 1,2-dithiins, (o-dithiin, 1,2-dithia-3,5-cyclohexadiene) and its derivatives, including 1,2-benzodithiins, benzo[c]-1,2-dithiins (2,3-benzodithiins), dibenzo[c,e]-1,2-dithiins, 3,4-dihydro-1,2-dithiins, and 3,6-dihydro-1,2-dithiins.
Color kinematic symmetric (BCJ) numerators in a light-like gauge

Color-ordered tree level scattering amplitudes in Yang-Mills theories can be written as a sum over terms which display the various propagator poles of Feynman diagrams. The numerators in these expressions which are obtained by straightforward application of Feynman rules are not satisfying any particular relations, typically. However, by reshuffling terms, it is known that one can arrive at a set of numerators which satisfy the same Jacobi identity as the corresponding color factors. By extending previous work by us we show how this can be systematically accomplished within a Lagrangian framework. We construct an effective Lagrangian which yields tree-level color-kinematic symmetric numerators in Yang-Mills theories in a light-like gauge at five-points. The five-point effective Lagrangian is non-local and it is zero by Jacobi identity. The numerators obtained from it respect the original pole structure of the color-ordered amplitude. We discuss how this procedure can be systematically extended to higher order.
Simple Catalytic Mechanism for the Direct Coupling of α-Carbonyls with Functionalized Amines: A One-Step Synthesis of Plavix

The direct α-amination of ketones, esters, and aldehydes has been accomplished via copper catalysis. In the presence of catalytic copper(II) bromide, a diverse range of carbonyl and amine substrates undergo fragment coupling to produce synthetically useful α-amino-substituted motifs. The transformation is proposed to proceed via a catalytically generated α-bromo carbonyl species; nucleophilic displacement of the bromide by the amine then delivers the α-amino carbonyl adduct while the catalyst is reconstituted. The practical value of this transformation is highlighted through one-step syntheses of two high-profile pharmaceutical agents, Plavix and amfepramone.
Calculable sparticle masses with radiatively driven inverted mass hierarchy

Abstract Supersymmetric models with an inverted mass hierarchy (IMH: multi-TeV first and second generation matter scalars, and sub-TeV third generation scalars) can ameliorate problems arising from flavor changing neutral currents, CP violating phases and electric dipole moments, while at the same time satisfying conditions on naturalness. It has recently been shown that such an IMH can be generated radiatively, making use of infra-red fixed point properties of renormalization group equations given Yukawa coupling unification and suitable GUT scale boundary conditions on soft SUSY breaking masses. In these models, explicit spectra cannot be obtained due to problems implementing radiative electroweak symmetry breaking (REWSB). We show that use of SO (10) D -term contributions to scalar masses can allow REWSB to occur, while maintaining much of the desired IMH. A somewhat improved IMH is obtained if splittings are applied only to Higgs scalar masses.
Synthesis and properties of 5‐(p‐carbomethoxyphenyl)‐ 15‐(p‐dimethylaminophenyl)porphyrin

An unsymmetrically substituted 5,15-diarylporphyrin 1, with p-dimethylamino and p-carbomethoxy substituents, was synthesized via a MacDonald condensation of aryldipyrromethane precursors 6 and 12, which were prepared in good yield by three or four step procedures starting from ethyl 3,4-dimethyl-1H-pyrrole-2-carboxylate (2).
Correlation and Cross-Linking Effects in Imprinting Sites for Divalent Adsorption in Gels†

We examine a method to mimic active sites in proteins by chemical imprinting of p-valent templates in heteropolymer gels. Previous studies have confirmed successful formation of sites by adsorption of targets with p >/= 2 contacts. We investigate the recovery of sites with p = 2 imprinted by lead methacrylate Pb(MAAc)(2) (placing two carboxyl groups in close proximity). The improved binding ability of gels with more cross-links, and the relative insensitivity to changes in gel volume contradict simple theory. We conclude that adsorber pairs are predominantly located on the same polymer chain, posing a challenge to mimicking protein-like function.
Formal Methods for Dynamical Systems

In control theory, "complex" models of physical processes, such as systems of differential equations, are usually checked against "simple" specifications, such as stability and set invariance. In formal methods, "rich" specifications, such as languages and formulae of temporal logics, are checked against "simple" models of software programs and digital circuits, such as finite transition graphs. With the development and integration of cyber physical and safety critical systems, there is an increasing need for computational tools for verification and control of complex systems from rich, temporal logic specifications. The formal verification and synthesis problems have been shown to be undecidable even for very simple classes of infinitespace continuous and hybrid systems. However, provably correct but conservative approaches, in which the satisfaction of a property by a dynamical system is implied by the satisfaction of the property by a finite over-approximation (abstraction) of the system, have received a lot of attention in recent years. Some classes of systems allowing for computationally efficient verification and control from temporal logic specifications are reviewed. For continuous and discrete-time linear systems and continuous-time multi-linear systems, it is shown that finite abstractions can be constructed through polyhedral operations only. By using techniques from model checking and automata games, this allows for verification and control from specifications given as Linear Temporal Logic (LTL) formulae over linear predicates in the state variables. A connection between the existence of Lyapunov functions and finite bisimulations is established for discrete-time linear and switched linear systems. Finally, optimality and correctness requirements are combined in a model predictive approach to generate control strategies for discrete-time linear systems. The usefulness of these computational tools is illustrated with various examples such as verification and synthesis of biological circuits in synthetic biology and motion planning and control in robotics.
Development of the 1,2-Oxaza-Cope Rearrangement

A method for a concise assembly of oxazine rings based on a Lewis acid-promoted hetero-Cope rearrangement is described. The hetero-Cope rearrangement features the first examples of the [3,3]-sigmatropic transpositions involving the nitroso group. A variety of functionalized substrates have been subjected to the reaction. The described method has a strong potential for the synthesis of marine natural products containing oxazine rings.
Electrohydrodynamically Coupled Minimum Film Boiling in Dielectric Liquids

The Zuber hypothesis for the minimum film boiling point as a hydrodynamic condition is modified to account for the effects of strong electrohydrodynamic coupling at the vapor-liquid interface surrounding a heated cylindrical wire when the interface is stressed by a strong nonuniform electric field. Different models for ac voltage highly insulating and ac/dc conducting fluid cases are proposed, based on charge relaxation effects. The models predict the effect of electrohydrodynamic coupling on dominant unstable wavelengths and heat flux values at the minimum film boiling condition. The ac voltage, highly insulating fluid model compares favorably with theory. The dc data do not deviate substantially from the ac data. Further, for both ac and dc voltages above some critical voltage, which depends on the heater wire radius, the appearance of the instability of the vapor film changes drastically, indicating an upper limit on the validity of the electrohydrodynamic model developed.
High-Resolution Structural Insights into Bone: A Solid-State NMR Relaxation Study Utilizing Paramagnetic Doping

The hierarchical heterogeneous architecture of bone imposes significant challenges to structural and dynamic studies conducted by traditional biophysical techniques. High-resolution solid-state nuclear magnetic resonance (SSNMR) spectroscopy is capable of providing detailed atomic-level structural insights into such traditionally challenging materials. However, the relatively long data-collection time necessary to achieve a reliable signal-to-noise ratio (S/N) remains a major limitation for the widespread application of SSNMR on bone and related biomaterials. In this study, we attempt to overcome this limitation by employing the paramagnetic relaxation properties of copper(II) ions to shorten the 1H intrinsic spin–lattice (T1) relaxation times measured in natural-abundance 13C cross-polarization (CP) magic-angle-spinning (MAS) NMR experiments on bone tissues for the purpose of accelerating the data acquisition time in SSNMR. To this end, high-resolution solid-state 13C CPMAS experiments were conducted on ...
Capital Income Taxes and Growth in a Stochastic Economy: A Numerical Analysis of the Role of Risk Aversion and Intertemporal Substitution

This paper undertakes a numerical analysis of the effects of changes in the tax rates on domestic and foreign capital income in a stochastically growing open economy under recursive preferences, in which the rate of time preference, ɛ, and the coefficient of risk aversion, R, can be set independently. The responses of the equilibrium growth rate, its volatility, and welfare to changes in the tax changes considered are highly sensitive to the independent variations in both ɛ and R. Consequently, the errors committed by using the conventional constant elasticity utility function, even for small violations of the compatibility condition (R= 1/ɛ) can be significant, suggesting that this functional form should be employed with caution.
Prediction of performance of two-phase flow nozzle and liquid metal magnetohydrodynamic (LMMHD) generator for no slip condition

Abstract Two-phase LMMHD energy conversion systems have potentially significant advantages over conventional systems, such as higher thermal efficiency and substantial simplicity with lower capital and maintenance costs. Maintenance of low velocity slip is of importance for achieving high generator efficiency. A bubbly flow pattern ensures very low velocity slip. The full governing equations have been written, and a computer prediction code has been developed to analyze the performance of a two-phase flow LMMHD generator and nozzle under conditions of no slip. Three different shapes of LMMHD generator have been investigated. Electrical power outputs are in the 20 kW range. Generator efficiency exceeds 71% at an average void fraction of about 70%. This is an appreciable performance for a short generator without insulating vanes for minimizing electrical losses in the end regions.
Reach-Scale Channel Geometry of a Mountain River

Mountain rivers can be subject to strong constraints imposed by changes in gradient and grain size supplied by processes such as glaciation and rockfall. Nonetheless, adjustments in the channel geometry and hydraulics of mountain rivers at the reach scale can produce discernible patterns analogous to those in fully alluvial rivers. Mountain rivers can differ in that imposed reach-scale gradient is an especially important control on reach-scale channel characteristics, as indicated by examination of North St Vrain Creek in Colorado. North St Vrain Creek drains 250 km2 of the Rocky Mountains. We used 25 study reaches within the basin to examine controls on reach-scale channel geometry. Variables measured included channel geometry, large woody debris, grain size, and mean velocity. Drainage area at the study reaches ranged from 2·2 to 245 km2, and gradient from 0·013 to 0·147 m m−1. We examined correlations among (1) potential reach-scale response variables describing channel bankfull dimension and shape, hydraulics, bedform wavelength and amplitude, grain size, ﬂow resistance, standard deviation of hydraulic radius, and volume of large woody debris, and (2) potential control variables that change progressively downstream (drainage area, discharge) or that are likely to reﬂect a reach-speciﬁc control (bed gradient). We tested the hypothesis that response variables correlate most strongly with local bed gradient because of the segmented nature of mountain channels. Results from simple linear regression analyses indicate that most response variables correlate best with gradient, although channel width and width/depth ratio correlate best with discharge. Multiple regression analyses using Mallow's Cp selection criterion and log-transformation of all variables produced similar results in that most response variables correlate strongly with gradient. These results suggest that the hypothesis is partially supported: channel bed gradient is likely to be a good predictor for many reach-scale response variables along mountain rivers, but discharge is also an important predictor for some response variables. Copyright © 2004 John Wiley & Sons, Ltd.
Forest fires, air pollution, and mortality in Southeast Asia

I assess the population health effects in Malaysia of air pollution from a widespread series of fires that occurred in Indonesia between April and November of 1997. I describe how the fires occurred and why the associated air pollution was so widespread and long lasting. The main objective is to uncover any mortality effects and to assess how large and important they were. I also investigate whether the mortality effects were persistent or whether they represented a short-term, mortality-harvesting effect. The results show that the smoke haze from the fires had a deleterious effect on the health of the population in Malaysia.
Functionalization of Diynes. Preparation of Bis(alkynyl) Ditosylate and Dibenzoate Esters and Bis(alkynyl) Dithiocyanates Via Alkynyl Iodonium Chemistry

Abstract The synthesis and characterization of the title compounds from the interaction of nucleophiles and bis[(phenyl) iodonium] diyne salts is described.
Sphingolipids as coenzymes in anion transfer and tumor death.

Abstract Many kinds of natural sphingolipids and their analogs stimulate or inhibit a wide assortment of biochemical phenomena and enzymes. The puzzle considered here is: how can these lipids control so many different kinds of processes? In almost every study in which a structural comparison was made, an allylic alcohol moiety [–CH CH–CH(OH)–] was found to be an essential feature of the sphingolipid. Many of those stimulations lead to cell death, emphasizing the importance of allylic sphingolipid structure in the design of chemotherapeutic agents. The proposal offered here is that these lipids function as coenzymes, in which the allylic moiety acts as an anion transferring agent, forming transient phosphate or acyl or peptidyl esters for the synthesis or hydrolysis of phosphoproteins, proteins, and phospholipids. Sphingolipids that inhibit these reactions may simply displace the active sphingolipids from their sites in the enzymes’ active regions, or bind to the enzymes’ allosteric region. This kind of competition could act as a major homeostatic control mechanism. Some of the allylic sphingolipids also generate reactive oxygen, possibly by oxidation of the allylic alcohol group. This explains the need to control redox-controlling metabolites in sphingolipid-controlled processes (e.g., glutathione). Many anticancer drugs that produce apoptosis in tumors possess an allylic alcohol residue, affect protein phosphorylation, and produce reactive oxygen species. They may be therapeutically useful because they control the action of sphingolipids as anion transfer agonists or inhibitors.
Associations between Hofstede’s Cultural Constructs and Social Desirability Response Bias

This paper examines the associations among social desirability response bias, cultural constructs and gender. The study includes the responses of 1537 students from 12 countries including Australia, Canada, China, Colombia, Ecuador, Hong Kong, Ireland, Japan, Nepal, South Africa, Spain, and the United States. The results of the analysis indicate that, on average, social desirability response bias decreases (increases) as a country’s Individualism (Uncertainty Avoidance) increases. The analysis also indicates that women scored significantly higher on Paulhus’ Image Management Subscale on an overall basis and for seven of the 12 country comparisons. This research serves as a caution when considering the research findings of prior international survey-based ethics research that do not include a direct measure of social desirability response bias. For example, the finding that women score higher on Paulhus’ measure of social desirability response bias calls into question prior research that does not control for social desirability response bias indicating women are more ethically sensitive than men.
High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator

The discovery of the quantum Hall (QH) effect led to the realization of a topological electronic state with dissipationless currents circulating in one direction along the edge of a two-dimensional electron layer under a strong magnetic field. The quantum anomalous Hall (QAH) effect shares a similar physical phenomenon to that of the QH effect, whereas its physical origin relies on the intrinsic spin-orbit coupling and ferromagnetism. Here, we report the experimental observation of the QAH state in V-doped (Bi,Sb)2Te3 films with the zero-field longitudinal resistance down to 0.00013 ± 0.00007h/e(2) (~3.35 ± 1.76 Ω), Hall conductance reaching 0.9998 ± 0.0006e(2)/h and the Hall angle becoming as high as 89.993° ± 0.004° at T = 25 mK. A further advantage of this system comes from the fact that it is a hard ferromagnet with a large coercive field (Hc > 1.0 T) and a relative high Curie temperature. This realization of a robust QAH state in hard ferromagnetic topological insulators (FMTIs) is a major step towards dissipationless electronic applications in the absence of external fields.
The carbocation continuum in terpene biosynthesis—where are the secondary cations?

In this tutorial review, structures encountered in carbocation cascade polycyclization reactions leading to terpene natural products are surveyed. The nature of delocalization in these carbocations is discussed in detail. For select cases, the ability of functional groups in enzyme active sites to modulate this delocalization is discussed. In addition to carbocation intermediates, cationic transition state structures are also described.
Critical groups of graphs with reflective symmetry

The critical group of a graph is a finite Abelian group whose order is the number of spanning forests of the graph. For a graph G with a certain reflective symmetry, we generalize a result of Ciucu---Yan---Zhang factorizing the spanning tree number of G by interpreting this as a result about the critical group of G. Our result takes the form of an exact sequence, and explicit connections to bicycle spaces are made.
Arc consistency for factorable relations

Abstract An optimal arc consistency algorithm AC-4 was given by Mohr and Henderson [8]. AC-4 has cost O( ed 2 ), and cost ( nd 2 ) for scene labelling. Although their algorithm is indeed optimal, under certain conditions a constraint satisfaction problem can be transformed into a less complex problem. In this paper, we present conditions and mechanisms for such representational transformations, and show how to factor relations into more manageable components. We describe how factorization can reduce AC-4's cost to O( ed ), and apply this result to RETE match. Further, with our factorization, the cost of scene labelling is reduced to O( nd ).
Synthesis of Amidomethyltrifluoroborates and Their Use in Cross-Coupling Reactions

Amidomethyltrifluoroborates were successfully synthesized in a one-pot fashion and used in cross-coupling reactions with a wide variety of aryl and heteroaryl chlorides.
Kelvin‐Helmholtz instability of the magnetopause of disc‐accreting stars

This work investigates the short-wavelength stability of the magnetopause between a rapidly rotating, supersonic, dense accretion disc and a slowly rotating low-density magnetosphere of a magnetized star. The magnetopause is a strong shear layer with rapid changes in the azimuthal velocity, the density and the magnetic field over a short radial distance and thus the Kelvin-Helmholtz (KH) instability may be important. The plasma dynamics are treated using non-relativistic, compressible (isentropic) magnetohydrodynamics. It is necessary to include the displacement current in order that plasma wave velocities remain less than the speed of light. We focus mainly on the case of a star with an aligned dipole magnetic field so that the magnetic field is axial in the disc midplane and perpendicular to the disc flow velocity. However, we also give results for cases where the magnetic field is at an arbitrary angle to the flow velocity. For the aligned dipole case, the magnetopause is most unstable for KH waves propagating in the azimuthal direction perpendicular to the magnetic field which tends to stabilize waves propagating parallel to it. The wave phase velocity is that of the disc matter. A quasi-linear theory of the saturation of the instability leads to a wavenumber (k) power spectrum ∝ k -1 of the density and temperature fluctuations of the magnetopause, and it gives the mass accretion and angular momentum inflow rates across the magnetopause. For self-consistent conditions, this mass accretion rate will be equal to the disc-accretion rate at large distances from the magnetopause.
Analysis of Fluid Flow Under a Grinding Wheel

Fluid flow under a grinding wheel is modeled using a perturbation scheme. In this initial effort to understand the flow characteristics, we concentrate on the case of a smooth wheel with slight clearance between the wheel and workpiece. The solution at lowest order is that given by standard lubrication theory. Higher-order terms correct for inertial and two-dimensional effects. Experimental and analytical pressure profiles are compared to test the validity of the model. Lubrication theory provides good agreement with low Reynolds number flows; the perturbation scheme provides reasonable agreement with moderate Reynolds number flows but fails at high Reynolds numbers. Results from experiments demonstrate that the ignored upstream and downstream conditions significantly affect the flow characteristics, implying that only a model based on the fully two- (or three-) dimensional Navier-Stokes equations will accurately predict the flow. We make one comparison between an experiment with a grinding wheel and the model incorporating a one-dimensional sinusoidal roughness term. For this case, lubrication theory surprisingly provides good agreement with experiment.