cssi/SciSciGPT-SciSciNet huggingface dataset:
A Convenient and Genuine Equivalent to HZrCp2Cl Generated in Situ from ZrCp2Cl2−DIBAL-H

Slow addition of 1 equiv of iBu2AlH to ZrCp2Cl2 in THF provides a convenient route to either HZrCp2Cl-iBu2AlCl (Reagent I) or HZrCp2Cl (Reagents II and III). The latter represents a highly convenient route to genuine HZrCp2Cl, while Reagent I is useful for regio- and stereoselective conversion of 1- and 2-alkynes into (E)-1-iodo-1-alkenes and (E)-2-iodo-2-alkenes, respectively.
The Role of “Allowable Flux Density” in the Design and Operation of Molten-Salt Solar Central Receivers

In the 1980s, the Utility Study [Hilesland, T., Jr., and Weber, E. R., 1988, Utilities' Study of Solar Central Receivers, Fourth Int. Symp. on Research, Development, and Applications of Solar Thermal Technology, Santa Fe, NM] identified the external cylindrical molten-salt-in-tube receiver with a surround heliostat field as the most cost effective and practical design for commercial applications. Such designs typically require 50-1000 MW of design-point thermal power at outlet temperatures around 1050°F (565°C). Using computer codes such as RCELL [Lipps, F. W., and Vant-Hull, L. L., 1978, A Cellwise Method for the Optimization of Large Central Receiver Systems, Solar Energy, 20(6) pp. 505-516.] or DELSOL [Kistler, B. L., A Users Manual for Delsol 3, Sandia National Laboratories Livermore, SAND86-8018, 1987.] it is straightforward to design an optical system to meet these requirements, defining the smallest receiver (lower cost and thermal losses) and the most cost effective heliostat field. As the performance of heliostats in the anti-sun locations is better such fields tend to be biased (in the northern hemisphere) to the north side of the receiver and produce very high flux densities there; typically 2-5 MW/m 2 . However, the receiver is typicaly limited to a salt velocity and temperature dependent allowable flux density (AFD) of about 1 MW/m 2 . Design methods to reduce this peak flux to a nominally acceptable value in a cost effective manner are presented. Residual excess flux events under non-nominal conditions are handled by a real-time processor which selects specific heliostats for removal from track. This same processor is used to preheat the receiver using a special algorithm to define the required flux density.
Does Foreign Military Intervention Help Human Rights

This article examines the effect of foreign armed intervention on human rights conditions in target countries. It is argued that military intervention contributes to the rise of state repression by...
Neutralino dark matter in mSUGRA/CMSSM with a 125 GeV light Higgs scalar

The minimal supergravity (mSUGRA or CMSSM) model is an oft-used frame- work for exhibiting the properties of neutralino (WIMP) cold dark matter (CDM). How- ever, the recent evidence from Atlas and CMS on a light Higgs scalar with mass $ {m_h} \simeq 125 $ GeV highly constrains the superparticle mass spectrum, which in turn constrains the neutralino annihilation mechanisms in the early universe. We find that stau and stop co-annihilation mechanisms — already highly stressed by the latest Atlas/CMS re- sults on SUSY searches — are nearly eliminated if indeed the light Higgs scalar has mass $ {m_h} \simeq 125 $ GeV. Furthermore, neutralino annihilation via the A-resonance is nearly ruled out in mSUGRA so that it is exceedingly difficult to generate thermally-produced neutralino-only dark matter at the measured abundance. The remaining possibility lies in the focus-point region which now moves out to $ {m_0} \sim 10 - 20 $ TeV range due to the required large trilinear soft SUSY breaking term A0. The remaining HB/FP region is more fine-tuned than before owing to the typically large top squark masses. We present updated direct and indirect detection rates for neutralino dark matter, and show that ton scale noble liquid detectors will either discover mixed higgsino CDM or essentially rule out thermally-produced neutralino-only CDM in the mSUGRA model.
Ultrasonic Wave Scattering by a Subsurface Flaw in Joined Fluid-Solid Half Spaces

The scattering of waves by a flaw (cavity or inclusion) that is embedded in an elastic half space at a finite depth below the interface with a fluid half space is studied using the T-matrix approach. Expressions are derived for the scattered fields generated in the fluid and solid half spaces as well as the asymptotic form of the field in the fluid at a large distance from the interface. Numerical results are presented for spherical voids and steel inclusions embedded in epoxy as well as oblate spheroidal voids in a metal for various flaw depths, scattering geometries, and frequency of the incident wave. The results obtained by keeping different orders of multiple scattering between the flaw and the interface are critically discussed.
Multiple stereocontrol using organotransition metal templates: Alkylation of enolates

Abstract Generation and alkylation of enolates from (5-oxocyclohexenyl)Mo(CO) 2 Cp complexes 1 and 3 was accomplished regio- and stereospecifically and in high yield, allowing the preparation of stereospecifically substituted cyclohexene derivatives.
Localized modes at a D-brane—O-plane intersection and heterotic Alice strings

We study a system of Nc D3-branes intersecting D7-branes and O7-planes in 1+1-dimensions. We use anomaly cancellation and string dualities to argue that there must be chiral fermion zero-modes on the D3-branes which are localized near the O7-planes. Away from the orientifold limit we verify this by using index theory as well as explicit construction of the zero-modes. This system is related to F-theory on K3 and heterotic matrix string theory, and the heterotic strings are related to Alice string defects in = 4 Super-Yang-Mills. In the limit of large Nc we find an AdS3 dual of the heterotic matrix string CFT.
Efficient Synthesis of Acylsilanes Using Morpholine Amides

A general synthesis of acylsilanes from the corresponding morpholine amides and silyllithium species is described. The use of morpholine amides is economical and prevents over-addition by the silyl nucleophile. The procedure cleanly affords acylsilanes in good yields and circumvents the use of stoichiometric copper(I) cyanide typically employed to synthesize these compounds from acid chlorides.
A Third Star in the T Tauri System.

New speckle holographic images of the T Tauri infrared companion (T Tauri IRC; T Tauri S) reveal it to be a double system with a sky-projected separation of 0. 05, corresponding to a linear distance of 7 AU.
Fabrication of fiber-reinforced celsian matrix composites

Abstract A method has been developed for the fabrication of small diameter, multifilament tow, fiber-reinforced ceramic matrix composites. Its application has been successfully demonstrated for the Hi-Nicalon/celsian system. Strong and tough celsian matrix composites, reinforced with BN/SiC-coated Hi-Nicalon fibers, have been fabricated by infiltrating the fiber tows with the matrix slurry, winding the tows on a drum, cutting and stacking of the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from the 0.75BaO–0.25SrO–Al 2 O 3 –2SiO 2 mixed precursor synthesized by solid state reaction from metal oxides. Hot pressing resulted in almost fully dense fiber-reinforced composites. The unidirectional composites having ∼42 vol.% of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of yield stress and strain were 435±35 MPa and 0.27±0.01%, respectively, and ultimate strengths of 900±60 MPa were observed. Young's modulus of the composites was measured to be 165±5 GPa.
One-pot catalytic asymmetric synthesis of pyranones.

Enantioenriched pyranones are important intermediates in the synthesis of natural products and the generation of compound libraries. A one-pot method for their synthesis is outlined. Catalytic asymmetric alkylation of 2-furfurals in the presence of catalytic (−)-MIB generates enantioenriched furyl zinc alkoxides. Addition of water/THF followed by NBS results in formation of pyranones with ee’s >90% and yields between 46−77%.
Structure in the Solar Corona from Radio Scintillation Measurements

Since the 1950s, a wide variety of radio observations based on scattering by electron density fluctuations in the solar wind has provided much of our information on density fluctuations and solar wind speed near the source region of the solar wind. This paper reviews recent progress in the understanding of the nature of these density fluctuations and their relationship to features on the Sun. The results include the first measurements of fine-scale structure within coronal streamers and evidence for structure in solar wind speed in the inner corona.
Paraelasticity, a mechanical analog of paramagnetism

Abstract O − 2 molecule ions can be substituted for halide ions in alkali halides. The internuclear axis has six equilibrium orientations namely, along the [110] axes of the crystal. In the unstressed crystal, all six orientations are equally populated. A mechanical stress applied to the host crystal lifts the sixfold orientational degeneracy and thus induces population differences that correspond to an alignment of the molecule-ions. This effect has been studied by means of paramagnetic resonance for uniaxial stress along [111], [110] and [100] and KC1, KBr and KI, in the temperature range between 1·5°K and 33°K. The experiments show that the distribution of the molecule-ions over the orientations that become nonequivalent through the stress is given by Boltzmann statistics, and that the energy differences occurring in the Boltzmann factors are proportional to the stress. The results are analyzed in terms of the continuum theory of lattice defects. The kinetics of the alignment and reorientation process was studied at and below 4·2°K. The O − 2 molecule-ions do not freeze in. The reorientation time τ at these low temperatures is inversely proportional to the absolute temperature and depends upon the host crystal and upon the stress axis. The dependence of τ on the stress axis can be understood in terms of two transition probabilities, one involving a 90° rotation of the molecule-ion in a (100)-type plane, the other a 60° rotation out of this plane.
Avalanches on a conical bead pile: scaling with tuning parameters

Uniform spherical beads were used to explore the scaling behavior of a granular system near its critical angle of repose on a conical 3D bead pile. We found two tuning parameters that could take the system to a critical point. The existence of those tuning parameters violates the fundamental assumption of self-organized criticality, which proposed that complex dynamical systems self-organize to a critical point without need for tuning. Our avalanche size distributions were well described by a simple power-law, as is characteristic of a critical point, with the power τ = 1.5 when dropping beads slowly onto the apex of a bead pile from a small height. However, we could also move the system from the critical point using either of two tuning parameters: the height from which the beads fell onto the top of the pile or the region over which the beads struck the pile. As the drop height increased, the system did not reach the critical point yet the resulting distributions were independent of the bead mass, coefficient of friction, or coefficient of restitution. All our apex-dropping distributions for any type of bead (glass, stainless steel, zirconium) showed universality by scaling onto a common curve with τ = 1.5 and σ = 1.0, where 1/σ is the power of the tuning parameter. From independent calculations using the moments of the distribution, we find values for τ = 1.6 ± 0.1 and σ = 0.91 ± 0.15. When beads were dropped across the surface of the pile instead of solely on the apex, then the system also moved from the critical point and again the avalanche size distributions fell on a common curve when scaled similarly using the same values of τ and σ. We also observed that an hcp structure on the base of the pile caused an emergent structure in the pile that had six faces with some fcc or hcp structure; this structure did not affect the distribution of avalanche sizes.
The Mythology of Prostitution: Advocacy Research and Public Policy

Over the past decade, public policies on prostitution and other types of sex work have been increasingly contested, both in academia and in popular debates. One perspective, the oppression paradigm, is increasingly reflected in media reporting on the sex industry and is steadily being articulated by government officials in the USA, Europe, and elsewhere. The proliferation of myths based on the oppression paradigm is responsible for the rise of a resurgent mythology of prostitution. This article examines the claims made by organizations, activists, and scholars who embrace the oppression paradigm, evaluates the reasoning and evidence used in support of their claims, and highlights some of the ways in which this perspective has influenced recent legislation and public policy in selected nations. The author presents an alternative perspective, the polymorphous paradigm, and suggests that public policy on prostitution would be better informed by this evidence-based perspective.
New Genera and Higher Taxa of Septate Gregarines (Protozoa, Apicomplexa)*

SYNOPSIS The following new taxa of septate gregarines are established: METAMERIDAE fam. nov. includes genera Metamera Duke, Deutomera Bhatia & Setna, and Cognettia gen. n., the last with the type and only species C. legeri (Cognetti de Martiis); family GREGARINIDAE Labbe includes Degiustia gen. n. with the type and only species D. hyallela (Batten & DeGiusti); Cirrigregarina gen. n., with the type species C. spissa (Henry) and another species, C. kamenote (Hoshide); and Molluskocystis gen. n., with the type and only species M. pterotracheae (Stuart). Family HIRMOCYSTIDAE (Grasse) includes Arachnocystis gen. n., with the type species A. arachnoidea (Devdhar & Gourishankar) and 3 other species A. nitida (Geus), A. oribatidae (Geus), A. scutovertexi (Erhardova). Family ACTINOCEPHALIDAE (Leger), subfamily Actinocephalinae (Leger), includes Chilogregarina gen. n., with the type species C. striata (Leger & Duboscq) and 3 other species C. brasiliensis (Pinto), C. dujardini (Schneider), and C. stella (Leger).
HEAT TRANSFER ANALYSIS OF RECEIVERS FOR A SOLAR CONCENTRATING COLLECTOR

Abstract The heat transfer characteristics and performance of conically wound, single-layer, monotube receivers for a concentrating solar collector are investigated. A discussion of methods and assumptions used to formulate the basic energy balances is presented. Results obtained from this analysis indicate the degree of sensitivity of performance lo variations in tube radius, inlet temperature, ambient temperature, absorptivity of the tube coating, and cone half-angle within receiver size and mounting limitations.
Effect of Modified Aerodynamic Strip Theories on Rotor Blade Aeroelastic Stability

Various existing unsteady aerodynamic strip theories which have been developed in the past for both fixed and rotary wing aeroelastic analyses are modified in the paper so as to make them applicable to the coupled flap-lag-torsional aeroelastic problem of a rotor blade in hover. These corrections are primarily due to constant angle of attack, constant inflow and variable free stream velocity due to lead-lag motion. Next, the modified strip theories are incorporated in a coupled flap-lag-torsional aeroelastic analysis of the rotor blade in hover and the sensitivity of the aeroelastic stability boundaries to the aerodynamic assumptions is examined.
The origin of the slow solar wind in coronal streamers

Abstract The highly variable slow solar wind has been associated with low-latitude regions of the heliosphere most clearly by the Ulysses spacecraft. Although, it is evident today that the slow solar wind originates in coronal helmet streamers, the mechanism of the slow solar wind acceleration, and the origin of the variability are still being debated. The combination of new observations and numerical modeling are beginning to address these questions. I will discuss how recent in-situ observations by Ulysses, white light and EUV observations by the LASCO and UVCS instruments on SOHO advanced our understanding of the streamer structure, dynamics, and stability. I will briefly review the current state of numerical MHD modeling of streamers, and the possible mechanisms that may produce the highly variable slow wind. I will present the results of recent heat-conductive MHD modeling of multiple streamer slow solar wind with heating function constrained by observations. I will show how multi-fluid numerical modeling of the slow solar wind in streamers helps to identify the regions of the slow solar wind outflow.
Innovation, Appropriability, And The Underpricing Of Initial Public Offerings

Using the information asymmetries theory of underpricing, we investigate the role of innovation in the underpricing of initial public offerings (IPOs). We develop and test a model in which patents reduce information asymmetries in industries where the link between patents and inventive returns is transparent, thereby reducing underpricing. Conversely, patents reflect increased information asymmetries and underpricing in industries where the link is not transparent. We examine these relationships in a sample of 1,413 IPOs and find strong support for our hypotheses. In so doing, we make an important theoretical contribution by showing that the IPO market contextualizes firm information. [ABSTRACT FROM AUTHOR] Copyright of Academy of Management Journal is the property of Academy of Management and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Quantum Dynamics of Polaron Formation

We calculate the real space and time formation of a polaron quasiparticle from a bare electron. The time-dependent Schr\"odinger equation for the Holstein model of electron-phonon coupling is numerically integrated in a large Hilbert space to obtain the time evolution of the electron and phonon densities and the electron-phonon (el-ph) correlation functions. The quantum dynamical nature of the phonons is preserved. As the el-ph coupling increases, qualitative changes in polaron formation occur when the one-phonon polaron bound state forms. A potential barrier between the quasifree and heavy polaron states exists in dimensions $D\ensuremath{\geqslant}2$, consistent with earlier adiabatic theory. We compare to recent experiments.
A Critical Reexamination of Default Logic, Autoepistemic Logic, and Only Knowing

Fifteen years of work on nonmonotonic logic has certainly increased our understanding of the area. However, given a problem in which nonmonotonic reasoning is called for, it is far from clear how one should go about modeling the problem using the various approaches. We explore this issue in the context on two of the best–known approaches, Reiter's default logic and Moore's autoepistemic logic, as well as two related notions of “only knowing,” due to Halpern and Moses and to Levesque. In particular, we return to the original technical definitions given in these papers and examine the extent to which they capture the intuitions they were designed to capture.
Synthetic Routes to Allenic Acids and Esters and Their Stereospecific Conversion to Butenolides.

The synthesis of allenic acids and esters and their conversion to butenolides has been examined in some detail. Racemic butenolides 10 are efficiently prepared from the esters 8 through treatment with BCl3 and exposure of the derived acid 9 to catalytic AgNO3 in acetone. Conversion of the enantioenriched allenylstannane (S)-17 to the acid 18 through lithiation and subsequent carboxylation with CO2 afforded racemic product. The enantioenriched propargylic mesylates 16 and 22 afforded the allenic esters 19 and 23 with inversion of configuration through treatment with Pd(Ph3P)4, CO, and the appropriate alcohol in THF. These reactions proceeded with ca. 10% or less of racemization. The allenic esters 23 yielded the iodobutenolides 24 by reaction with IBr. Hydrogenolysis to the butenolide 25 was achieved with Pd(PPh3)4 and Bu3SnH. Alternatively, the allenic acids 27 could be prepared directly from mesylates 22 with Pd(PPh3)4 and CO in aqueous THF. Cyclization to the butenolides 25 was achieved, as before, with...
Intramolecular ene reactions of 1,7-octenynes: The involvement of 1,2-cyclooctadiene intermediates

Abstract 1,2-Cyclooctadienes are proposed as intermediates in the intramolecular ene cyclization of acyclic 1,7-octenyne derivatives.
Quanta of geometry and rotating black holes

In the loop approach to quantum gravity the spectra of operators corresponding to such geometrical quantities as length, area and volume become quantized. However, the size of arising quanta of geometry in Planck units is not fixed by the theory itself: a free parameter, sometimes referred to as the Immirzi parameter, is known to affect the spectrum of all geometrical operators. In this paper I propose an argument that fixes the value of this parameter. I consider rotating black holes, in particular the extremal ones. For such black holes the `no naked singularity condition' bounds the total angular momentum J by , where is the horizon area and G is Newton's constant. A similar bound on J comes from the quantum theory. The requirement that these two bounds are the same fixes the value of the Immirzi parameter to be unity. A byproduct of this argument is a picture of the quantum extremal rotating black hole in which all the spin entering the extremal hole is concentrated in a single puncture.
Coupling spans of the Higgs-like boson

Using the LHC and Tevatron data, we set upper and lower limits on the total width of the Higgs-like boson. The upper limit is based on the well-motivated assumption that the Higgs coupling to a W or Z pair is not much larger than in the Standard Model. These width limits allow us to convert the rate measurements into ranges for the Higgs couplings to various particles. A corollary of the upper limit on the total width is an upper limit on the branching fraction of exotic Higgs decays. Currently, this limit is 47% at the 95% CL if the electroweak symmetry is broken only by doublets.
Genetic factors in the control of brain levels of biogenic amines and brain excitability

Brain concentrations of DA, NE and 5HT are highly constant for a given mouse strain. However there are large differences in amine levels in different strains and amine profiles of the three amines are unique to a given strain. All three amines are high in high amine strains and low in low amine strains. F1 crosses of ICR, C57B16 and BALB mice gave amine levels that are the mean of the levels in the parent strains suggesting an isogenetic inheritance of brain amine level control. Electroshock seizure latency and threshold are markedly higher in high brain amine strains suggesting a role of the biogenic amines as an inhibitory system in the control of brain excitability.
Modular synthesis of N-vinyl benzotriazoles.

A modular approach to N1-vinyl benzotriazoles by azide–aryne cycloadditions and Julia–Kocienski reactions is described. Reactions of azidomethyl phenyl-1H-tetrazol-5-yl (PT) sulfide with arynes gave methyl(PT-sulfanyl)-substituted benzotriazoles in 68–89% yields. Oxidation of the sulfides to the sulfones gave the benzotriazole-substituted Julia–Kocienski reagents. Olefination reactions of aldehydes and a ketone with reagents derived from benzyne, 2,3-naphthyne, and 4,5-dimethoxybenzyne precursors proceeded to give various N1-vinyl benzotriazole derivatives. Olefination stereoselectivities are tunable for electron-rich aldehydes, but not for electron-deficient aldehydes and alkanals, where they proceed with good to excellent Z-stereoselectivity.
Impingement tones of large aspect ratio supersonic rectangular jets

The frequency structure of large aspect ratio jet impingement tones is analyzed. Feedback loops consisting of downstream propagating instability waves of the jet flow and upstream propagating acoustic waves from the wall to the nozzle lip produce as many as 20 or more tones when a supersonic rectangular jet of large aspect ratio is directed normal on a wall. It is seen that there are only two basic tones. The basic tone of the lower frequency is associated with a symmetric instability feedback mode of the jet, while that of the higher frequency is associated with an antisymmetric instability feedback mode. The remaining tones are combination tones of the two basic frequencies and their harmonics. It is determined that the measured basic impingement tone frequencies fall in the theoretical permissible frequency bands over a wide range of jet Mach number.
Family Planning Programs, Socioeconomic Characteristics, and Contraceptive Use in Malawi

Abstract In this paper, micro-level data from a survey of 4,849 women in Malawi are linked to information from a service availability questionnaire to assess the relative importance of socioeconomic background and various aspects of family planning provision on contraceptive use in one country in sub-Saharan Africa. Maximum-likelihood probit is used to assess the independent influence of four distinct dimensions of family planning effort on contraceptive use: mass media exposure, i.e., promotion of family planning through radio and print messages; contraceptive choice; accessibility of contraceptive services; and service quality. Results indicate that all four components of family planning effort contribute to the use of modern contraceptives in Malawi, although their relative importance varies significantly across different segments of the population.
On the correlations of trend-cycle errors ✩

Abstract This note provides explanations for an unexpected result, namely, the estimated parameter of the correlation coefficient of the trend shock and cycle shock in the state–space model is almost always (positive or negative) unity, even when the true variance of the trend shock is zero. It is shown that the set of the true parameter values lies on the restriction that requires the variance–covariance matrix of the errors to be nonsingular, therefore, almost always the likelihood function has its (constrained) global maximum on the boundary where the correlation coefficient implies perfect correlation.
Hypervalent iodine nitrene precursors bearing N-heterocyclic rings

Novel nitrene precursors of the form PhINSO2R (R = 1-methylimidazolyl (1), pyridine (2), 2-pyridine N-oxide (3)) have been prepared that contain heterocyclic sulfonamide residues. These new iodinanes are evaluated as sources of the corresponding heterocycle-containing nitrenes in aziridination and sulfimidation reactions.
Vector operators in the BMN correspondence

We consider a BMN operator with one scalar, and one vector, DμZ, impurity field and compute the anomalous dimension both at planar and torus levels. This mixed operator corresponds to a string state with two creation operators which belong to different SO(4) sectors of the background. The anomalous dimension at both levels is found to be the same as the scalar impurity BMN operator. At planar level this constitutes a consistency check of BMN conjecture. Agreement at the torus level can be explained by an argument using supersymmetry and supression in the BMN limit. The same argument implies that a class of fermionic BMN operators also have the same planar and torus level anomalous dimensions. Implications of the results for the map from = 4 SYM theory to string theory in the pp-wave background are discussed.
Advance in a nano-accuracy surface profiler with an extended-angle test range

Abstract An advanced design of a nano-accuracy surface profiler (NSP) is introduced wherein we combined a scanning optical head with non-tilted reference system to facilitate measurements over an extended range of angles. The lateral motion of the beam during testing of a strongly curved mirror induces a systematic error. For a pencil-beam scanning profiler, the arm with varying optical-path lengths should be non-tilted so to eliminate the beam's lateral motion, and the arm for testing larger angles should be short and fixed so to reduce the beam's lateral motion. Our new scheme of having a non-tilted reference system offers an effective, simple, and convenient solution. A beam spot of 0.5–1 mm is used for higher spatial frequency tests in surface-figure measurements. Some preliminary studies and test are demonstrated.
Pd(II)-catalyzed hydroxyl-directed C-H activation/C-O cyclization: expedient construction of dihydrobenzofurans.

A Pd(II)-catalyzed C−H activation/C−O cyclization reaction directed by a proximate hydroxyl group has been developed. This reaction provides a new method for constructing dihydrobenzofurans, including spirocyclic analogues, a process that is potentially applicable to natural product synthesis.
Computational Simulation of Emission Spectra from Shock-Layer Flows in an Arcjet Facility

This paper reports computational comparisons with experimental studies of a nonequilibrium bluntbody shock-layer e ow in a high-enthalpy arcjet wind tunnel at NASA Ames Research Center. The experimental data include spatially resolved emission spectra of radiation emanating from a shock layer formed in front of a e at-faced cylinder model. Multitemperature nonequilibrium codes are used to compute the conical nozzle e ow, supersonic jet, and shock-layer e ow. A line-of-sight (LOS) radiation code is employed to predict the spectra from the computed e owe eld. Computed LOS emission intensities are directly compared with the experimental data at several axial locations along the stagnation streamline. Various LOS-averaged e ow properties, such as vibrational and rotational temperatures, and species number densities, deduced from the experimental spectra, are compared with computed results. Comparisons provide an assessment of thermochemical equilibration processes in an arcjet shock layer.
Side-chain and backbone ordering in homopolymers.

In order to study the relation between backbone and side-chain ordering in proteins, we have performed multicanonical simulations of deka-peptide chains with various side groups. Glu10, Gln10, Asp10, Asn10, and Lys10 were selected to cover a wide variety of possible interactions between the side chains of the monomers. All homopolymers undergo helix−coil transitions. We found that peptides with long side chains that are capable of hydrogen bonding, i.e., Glu10, and Gln10, exhibit a second transition at lower temperatures connected with side-chain ordering. This occurs in the gas phase as well as in solvent, although the character of the side-chain structure is different in each case. However, in polymers with short side chains capable of hydrogen bonding, i.e., Asp10 and Asn10, side-chain ordering takes place over a wide temperature range and exhibits no phase transition-like character. Moreover, non-backbone hydrogen bonds show enhanced formation and fluctuations already at the helix−coil transition temp...
Probabilistic Simulation of Fragment Dynamics and Their Surface Impacts in the SSME Turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high pressure fuel turbopump of the space shuttle main engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.
A Central Limit Theorem for Weighted Averages of Spins in the High Temperature Region of the Sherrington-Kirkpatrick Model

In this paper we prove that in the high temperature region of the Sherrington-Kirkpatrick model for a typical realization of the disorder the weighted average of spins $\sum_{i \leq N} t_i \sigma_i$ will be approximately Gaussian provided that $\max_{i \leq N}|t_i|/\sum_{i \leq N} t_i^2$ is small.
Thermal force induced by the presence of a particle near a solidifying interface.

The presence of a foreign particle in the melt, ahead of a solid-liquid interface, leads to the onset of interfacial deformations if the thermal conductivity of the particle, k(p), differs from that of the melt, k(l). In this paper, the influence of the thermal conductivity contrast on the interaction between the solidifying interface and the particle is quantified. We show that the interface distortion gives rise to a thermal force whose expression is given by F(th)=2piLGa3(1-alpha)/(2+alpha)T(m), where L is the latent heat of fusion per unit volume, T(m) is the melting point, a is the particle's radius, G the thermal gradient in the liquid phase and alpha=k(p)/k(l). The derivation makes use of the following assumptions: (i) the particle is small compared to the horizontal extent of the interface, (ii) the particle is placed in the near proximity of the deformable solid-liquid interface, and (iii) the interface is practically immobile in the calculation of the thermal field, i.e., V<<k(l)G/L, where V is the interface growth velocity. An order of magnitude analysis shows that the magnitude of the thermal force may be greater than that of the forces that are usually accounted for in studies of particle-interface interaction, namely, the drag force and the force due to the disjoining pressure. The inclusion of the thermal force in the overall force balance is found to modify the value of the growth rate at which equilibrium is attained. The analysis leads to the prediction that the growth rate at equilibrium is increased for particles with a low thermal conductivity and is decreased for particles with a high thermal conductivity. The derivation of the thermal force is preceded by a detailed analysis of the influence of the thermal conductance contrast on the interface profile.
Role of symmetry in Raman spectroscopy of unconventional superconductors

ABSTRACT The role of symmetry of the inelastic light scattering amplitude, the superconducting energy gap, and the underlying Fermi surface manifold on the Raman spectra of unconventional superconductors is discussed in detail. Particular emphasis is placed on both single and bi-layer superconductors. It is found that the B19 channel may be the most sensitive to doping due to the role of the Van Hove singularity. Lastly the effect of both disorderand spin fluctuations is considered. The theory imposes strong constraints on both the magnitude and symmetryof the energy gap for the bi-layer cuprates, indicating that a nearly identical energy gap of symmetry provides a best fit to the data. Keywords: Raman scattering, unconventional superconductivity, bi-layer, spin fluctuations, impurities. 1 Introduction In the recent few years Raman scattering has been proved to be a very powerful tool to study the anisotropy ofthe superconducting energy gap in high T superconductors. The rich information provided from experiments lies
Composition of individual particles in the wakes of an Athena II rocket and the space shuttle

[1] The Particle Analysis by Laser Mass Spectrometry (PALMS) instrument was used to obtain the first in situ measurements of the composition of particles in the wakes of solid rocket motor (SRMs) launch vehicles. PALMS acquired mass spectra of over 2300 exhaust particles within the plumes of an Athena II rocket and the Space Shuttle. The majority of positive spectra indicated the presence of primary and trace components of the aluminum fuel and the combustion catalyst. Negative spectra showed chlorine from the oxidizer. Nitrate and phosphate fragments and water were common features of spectra acquired during the Space Shuttle encounters. Elemental carbon (EC) was a significant particle type observed in the Athena II plume. The data show that particles emitted by SRMs are more diverse and probably more reactive than previously considered.
A transition-state model for the mikami enantioselective ene reaction

Abstract A logically derived mechanistic model is presented for the Mikami enantioselective ene reaction which correctly describes the absolute and relative stereochemistry resulting from transition-state structures such as 3 and 5.
MULTI-SCALE ISO-SURFACE EXTRACTION FOR VOLUME VISUALIZATION

This paper describes a new multi-scale approach for the extraction of iso-surfaces from volume datasets. The goal is to automatically identify iso-surfaces that best approximate the boundary surfaces at different levels of details. Using histogram analysis, iso-values are extracted from histograms of boundary voxels defined by gradient thresholding or zero-crossing boundaries. Multi-scale smoothing of the histogram using Gaussian filters of various sizes allows the iso-surfaces to be defined hierarchically over a scale space map. It provides an interactive environment and volume navigation tools for the exploration of large volume datasets by visualizing the layers of the volume space in a multi-scale manner.
Postoperative jejunal feeding and outcome of pancreaticoduodenectomy.

Complications following pancreaticoduodenectomy are common, partly because of nutritional debilitation. The aim of this study was to evaluate the impact of early postoperative tube feeding on outcome of pancreaticoduodenectomy and determine the best method for delivering enteral feeding. A retrospective review of 180 consecutive patients undergoing Whipple operations from 1994 to 2000 was performed. Two nonrandomized patient groups were retrospectively studied: those with early postoperative tube feeding vs. those with no planned feeding. Ninety-eight patients (54%) received postoperative jejunal feeding, whereas 82 patients (46%) did not. Jejunal feeding was delivered via a bridled nasojejunal tube in 55 patients (56%) and a gastrojejunal tube in 43 (44%). Vomiting (10% vs. 29%; P = 0.002) and use of total parenteral nutrition (6% vs. 27%; P < 0.0001) were less in the jejunal feeding group as well as rates of readmission (12% vs. 27%; P = 0.022), early (52% vs. 62%; P = 0.223) and late (12% vs. 31%, P = 0.005) complications, and infections (13% vs. 20%, P = 0.014). Tube-related complications occurred in 6 of 98 patients, all of which were associated with gastrojejunal tubes (P = 0.021). Early postoperative tube feeding after pancreaticoduodenectomy is associated with significantly less use of total parenteral nutrition and lower rates of readmission and complications. A bridled nasojejunal feeding tube appears to be a safe and reliable method of short-term enteral feeding.
Asymptotics of Recurrence Relation Coefficients, Hankel Determinant Ratios, and Root Products Associated with Laurent Polynomials Orthogonal with Respect to Varying Exponential Weights

Let Λℝ denote the linear space over ℝ spanned by zk, k∈ℤ. Define the real inner product 〈⋅,⋅〉L:Λℝ×Λℝ→ℝ, \((f,g)\mapsto \int_{\mathbb{R}}f(s)g(s)\exp (-{N}V(s))\mathop {d}s\) , N∈ℕ, where V satisfies: (i) V is real analytic on ℝ∖{0}; (ii) lim |x|→∞(V(x)/ln (x2+1))=+∞; and (iii) lim |x|→0(V(x)/ln (x−2+1))=+∞. Orthogonalisation of the (ordered) base \(\lbrace 1,z^{-1},z,z^{-2},z^{2},\ldots ,z^{-k},z^{k},\ldots \rbrace\) with respect to 〈⋅,⋅〉L yields the even degree and odd degree orthonormal Laurent polynomials (OLPs) \(\lbrace \phi_{m}(z)\rbrace_{m=0}^{\infty}\) : φ2n(z)=∑k=−nnξk(2n)zk, ξn(2n)>0, and φ2n+1(z)=∑k=−n−1nξk(2n+1)zk, ξ−n−1(2n+1)>0. Associated with the even degree and odd degree OLPs are the following two pairs of recurrence relations: zφ2n(z)=c2n♯φ2n−2(z)+b2n♯φ2n−1(z)+a2n♯φ2n(z)+b2n+1♯φ2n+1(z)+c2n+2♯φ2n+2(z) and zφ2n+1(z)=b2n+1♯φ2n(z)+a2n+1♯φ2n+1(z)+b2n+2♯φ2n+2(z), where c0♯=b0♯=0, and c2k♯>0, k∈ℕ, and z−1φ2n+1(z)=γ2n+1♯φ2n−1(z)+β2n+1♯φ2n(z)+α2n+1♯φ2n+1(z)+β2n+2♯φ2n+2(z)+γ2n+3♯φ2n+3(z) and z−1φ2n(z)=β2n♯φ2n−1(z)+α2n♯φ2n(z)+β2n+1♯φ2n+1(z), where β0♯=γ1♯=0, β1♯>0, and γ2l+1♯>0, l∈ℕ. Asymptotics in the double-scaling limit N,n→∞ such that N/n=1+o(1) of the coefficients of these two pairs of recurrence relations, Hankel determinant ratios associated with the real-valued, bi-infinite strong moment sequence \(\lbrace c_{k}=\int_{\mathbb{R}}s^{k}\exp (-{N}V(s))\mathop {d}s\rbrace_{k\in \mathbb{Z}}\) , and the products of the (real) roots of the OLPs are obtained by formulating the even degree and odd degree OLP problems as matrix Riemann-Hilbert problems on ℝ, and then extracting the large-n behaviours by applying the non-linear steepest-descent method introduced in (Ann. Math. 137(2):295–368, [1993]) and further developed in (Commun. Pure Appl. Math. 48(3):277–337, [1995]) and (Int. Math. Res. Not. 6:285–299, [1997]).
Bent waveguides for matter-waves: supersymmetric potentials and reflectionless geometries

Non-zero curvature in a waveguide leads to the appearance of an attractive quantum potential which crucially affects the dynamics in matter-wave circuits. Using methods of supersymmetric quantum mechanics, pairs of bent waveguides are found whose geometry-induced potentials share the same scattering properties. As a result, reflectionless waveguides, dual to the straight waveguide, are identified. Strictly isospectral waveguides are also found by modulating the depth of the trapping potential. Numerical simulations are used to demonstrate the efficiency of these approaches in tailoring and controlling curvature-induced quantum-mechanical effects.
Congeners of Troeger's base as chiral ligands

Abstract ( S )-(+)-Troeger's base can be deprotonated and alkylated without loss of stereochemical integrity. An examination of the ability of Troeger's base and several derivatives prepared in this fashion to effect asymmetric induction in the addition of diethylzinc to aromatic aldehydes was conducted. Enantiomeric excesses as high as 86% were achieved, providing evidence that Troeger's base represents a chiral framework which can be modified to produce ligands for catalytic asymmetric synthesis.
QRIS research: Looking back and looking forward

Abstract In this commentary, we discuss the current state of QRIS research and evaluation, expectations for the research currently under way, and aspirations for the future of QRIS research. By reviewing the types of submissions received for the special issue and addressing methodological and conceptual gaps, we aim to help researchers and their partners fill these gaps and make future contributions to research and practice.
Constraints on extended neutral gauge structures

Indirect precision data are used to constrain the masses of possible extra Z′ bosons and their mixings with the ordinary Z. We study a variety of Z′ bosons as they appear in E6 and left-right unification models, the sequential Z boson, and the example of an additional U(1) in a concrete model from heterotic string theory. In all cases the mixings are severely constrained (sinθ<0.01). The lower mass limits are generally of the order of several hundred GeV and competitive with collider bounds. The exception is the Zψ boson, whose vector couplings vanish and whose limits are weaker. The results change little when the ρ parameter is allowed, which corresponds to a completely arbitrary Higgs sector. On the other hand, in specific models with minimal Higgs structures the limits are generally pushed into the TeV region.
Vibrational spectra of Mg(OH)2 and Ca(OH)2 under pressure

The effects of compression on the structure and bonding of Mg(OH)2 brucite and Ca(OH)2 portlandite are documented to pressures of 34 and 24 GPa, respectively, by way of infrared spectroscopy of the O–H stretching vibration at 300 K. The frequency of the infrared‐active (A2u) mode of both hydroxides decreases with pressure, by −0.6 cm−1/GPa for Mg(OH)2 over the pressure range studied, and by −3.5 cm−1/GPa for Ca(OH)2 to 10.6 GPa. An additional mode observed in Mg(OH)2 is due to an optically induced hot band (A2u X A2u overtone): with increasing pressure, its intensity grows and its frequency decreases (−3.7 cm−1/GPa). The negative pressure dependencies of these modes (negative Gruneisen parameters) are explained in terms of compression increasing the hydrogen bond strength within the hydroxide structure. On increasing pressure above 12.8 GPa, the full width at half‐maximum of the O–H vibration in Ca(OH)2 rapidly broadens by a factor of 4. The infrared data suggest that Ca(OH)2 undergoes pressure‐induced am...
Vortex ring refraction at large Froude numbers.

We have experimentally studied the impact of an initially planar axisymmetric vortex ring, incident at an oblique angle, upon a gravity-induced interface separating two fluids of differing densities. After impact, the vortex ring was found to exhibit a variety of subsequent trajectories, which we organize according to both the incidence angle, ${\ensuremath{\theta}}_{i}$, and the interface strength, defined as the ratio of the Atwood and Froude numbers, $A/F$. For grazing incidence angles $({\ensuremath{\theta}}_{i}\ensuremath{\gtrsim}70\ifmmode^\circ\else\textdegree\fi{})$ vortices either penetrate or reflect from the interface, depending on whether the interface is weak or strong. In some cases, reflected vortices execute damped oscillations before finally disintegrating. For smaller incidence angles $({\ensuremath{\theta}}_{i}\ensuremath{\lesssim}70\ifmmode^\circ\else\textdegree\fi{})$ vortices penetrate the interface. When there is a strong interface, these vortices are observed to curve back up toward the interface. When there is a weak interface, these vortices are observed to refract downward, away from the interface. The critical interface strength below which vortex ring refraction is observed is given by ${\text{log}}_{10}(A/F)=\ensuremath{-}2.38\ifmmode\pm\else\textpm\fi{}0.05$.
Diffuse X-ray emission from the planetary nebula NGC 7009

XMM-Newton EPIC observations of the planetary nebula (PN) NGC 7009, the Saturn Nebula, have detected extended X-ray emission in its central cavity. The diffuse X-ray emission must originate in the shocked fast stellar wind. The spectra show that the temperature of the hot gas is $1.8\times 10^6$ K. The rms density derived from the volume emission measure is a few tens H-atom cm -3 . The hot gas does not appear over-pressurized with respect to the nebular shell. NGC 7009 represents an evolutionary stage at which the influence of the hot gas in the PN interior starts to decline due to the diminishing strength of the fast stellar wind and the expansion of the central cavity.
Hydrocarbon oxidation catalyzed by self-folded metal-coordinated cavitands.

Functionalized cavitands have been shown to self-fold via coordination of Fe(II) salts and effect catalytic C–H oxidation reactions of unfunctionalized alkanes under mild aqueous conditions in the presence of tert-butyl hydroperoxide as co-oxidant. Secondary and tertiary C–H bonds can be converted to ketones and alcohols, respectively, and ethers can be converted to esters. The cavitands retain the catalytic metal throughout the reaction, and can be recovered by filtration.
Comparing Linear and Essentially Nonlinear Vibration-Based Energy Harvesting

This work considers the performance of a resonant vibration-based energy harvesting system utilizing a strongly nonlinear attachment. Typical designs serving as the basis for harvesting energy from ambient vibration typically employ a linear oscillator for this purpose, limiting peak harvesting performance to a narrow band of frequencies about the resonant frequency of the oscillator. Herein, in an effort to maximize performance over the broader band of frequency content typically observed in ambient vibration measurements, we employ an essentially nonlinear cubic oscillator in the harvesting device and show that, with proper design, significant performance gains can be realized as compared with a tuned linear attachment. However, we also show that the coexistence of multiple equilibria due to the nonlinearity can degrade system performance, as the system can be attracted to a low amplitude state that provides reduced harvested power. Finally when multiple equilibria exist in the system, the basins of attraction for the stable states are determined and related to the expected response of the system.