cssi/SciSciGPT-SciSciNet huggingface dataset:
Development and evaluation of a web-based assent for adolescents considering an HIV vaccine trial

HIV vaccine trials with minors will likely require parental permission and informed assent from adolescents. For this to be a valid process, the information needs to be presented in a manner that promotes adolescent comprehension. Previous studies suggest that adolescent comprehension of assent is often insufficient. We developed an interactive web-based assent that included interspersed quiz questions for a hypothetical HIV vaccine trial. Efficacy of the web-based assent was compared to a standard paper assent with and without interspersed questions. One hundred twenty teen participants, ages 15-17 years, from five community organizations were randomized to self-administered web-based assent (n=60) or investigator-administered paper assent with (n=29) or without (n=31) interspersed quiz questions. After reviewing the assent, participants completed a 27-item comprehension test. Comprehension scores were compared between groups. The mean number of correctly answered questions were 21.2 for the full paper group and 21.1 for the web-based group (t118=-0.08, p=0.94). Scores were 20.2 for the paper without interspersed questions sub-group and 22.1 for the paper with interspersed questions sub-group (t58=1.96, p=0.055). Participants in the web-based group performed as well on the comprehension test as those in the paper group, and those in the paper with questions sub-group performed better than those in the paper without questions sub-group, suggesting that interspersed quiz questions may improve understanding of a traditional paper assent. The minimal investigator time and standardized administration of the web-based assent as well as ability to tailor the assent discussion to topics identified by incorrect comprehension test responses are advantages worthy of further investigation.
The critical independence number and an independence decomposition

An independent set I"c is a critical independent set if |I"c|-|N(I"c)|>=|J|-|N(J)|, for any independent set J. The critical independence number of a graph is the cardinality of a maximum critical independent set. This number is a lower bound for the independence number and can be computed in polynomial time. Any graph can be efficiently decomposed into two subgraphs where the independence number of one subgraph equals its critical independence number, where the critical independence number of the other subgraph is zero, and where the sum of the independence numbers of the subgraphs is the independence number of the graph. A proof of a conjecture of Graffiti.pc yields a new characterization of Konig-Egervary graphs: these are exactly the graphs whose independence and critical independence numbers are equal.
Higgs phenomenon for the graviton in ADS space

In this review, we summarize recent findings that show how standard 4D Einstein gravity coupled to a conformal field theory can become massive in anti de Sitter space. Key ingredients in this phenomenon are nonstandard "transparent" boundary condition given to the CFT fields and the fact that AdS space is not globally hyperbolic, due to the presence of a time-like boundary.
An Experimenter's View of Lattice QCD

Lattice QCD has the potential this decade to maximize the sensitivity of the entire flavor physics program to new physics and pave the way for understanding physics beyond the Standard Model at the LHC in the coming decade. However, the challenge for the Lattice is to demonstrate reliability at the level of a few per cent given a past history of 10-20% errors. The CLEO-c program at the Cornell Electron Storage Ring is providing the data that will make the demonstration possible.
The symmetry of intersection numbers in group theory

For suitable subgroups of a nitely generated group, we dene the intersection number of one subgroup with another subgroup and show that this number is symmetric. We also give an interpretation of this number.
Statistical Modeling of RNA-Seq Data

Recently, ultra high-throughput sequencing of RNA (RNA-Seq) has been developed as an approach for analysis of gene expression. By obtaining tens or even hundreds of millions of reads of transcribed sequences, an RNA-Seq experiment can offer a comprehensive survey of the population of genes (transcripts) in any sample of interest. This paper introduces a statistical model for estimating isoform abundance from RNA-Seq data and is flexible enough to accommodate both single end and paired end RNA-Seq data and sampling bias along the length of the transcript. Based on the derivation of minimal sufficient statistics for the model, a computationally feasible implementation of the maximum likelihood estimator of the model is provided. Further, it is shown that using paired end RNA-Seq provides more accurate isoform abundance estimates than single end sequencing at fixed sequencing depth. Simulation studies are also given.
COMPLETENESS OF IMAGING SURVEYS FOR ECCENTRIC EXOPLANETS

The detection of exoplanets through direct imaging has produced numerous new positive identifications in recent years. The technique is biased toward planets at wide separations due to the difficulty in removing the stellar signature at small angular separations. Planets in eccentric orbits will thus move in and out of the detectable region around a star as a function of time. Here we use the known diversity of orbital eccentricities to determine the range of orbits that may lie beneath the detection threshold of current surveys. We quantify the percentage of the orbit that yields a detectable signature as a function of semimajor axis, eccentricity, and orbital inclination and estimate the fraction of planets which likely remain hidden by the flux of the host star.
Critical Behavior of a Classical Heisenberg Ferromagnet with Many Degrees of Freedom

The critical behavior of a classical Heisenberg ferromagnet is studied in the limit where the spin dimensionality $N$ is large. Corrections of order $\frac{1}{N}$ to the spherical model are obtained as functions of a continuous dimension $d$, $2<d<4$. Particular attention is given to the behavior near the coexistence curve. The divergence of the magnetic susceptibility below ${T}_{c}$ as the external field vanishes is discussed through a nonlinear realization of the $O(N)$ symmetry, as well as in the $\frac{1}{N}$ and $4\ensuremath{-}d$ expansions.
Stable disequilibrium prices

Abstract In an economy with non-convex production possibility sets the Walrasian adjustment process is well-defined. Under appropriate conditions it is globally stable with a limit which is not a competitive equilibrium and is a non-market-clearing price. This limit is the competitive equilibrium price vector of the economy obtained by convexification of the production sets.
The Nature of Surface CrOx Sites on SiO2 in Different Environments

This perspective article critically reviews the catalysis literature on the nature of the surface CrOx sites present on SiO2 in different environments. The recent application of in situ spectroscopic techniques that directly monitor the surface chromia sites on silica in different environments has significantly improved our fundamental understanding of supported CrOx/SiO2 catalysts.
Effects of pressure gradients on turbulent premixed flames

In most practical situations, turbulent premixed flames are ducted and, accordingly, subjected to externally imposed pressure gradients. These pressure gradients may induce strong modifications of the turbulent flame structure because of buoyancy effects between heavy cold fresh and light hot burnt gases. In the present work, the influence of a constant acceleration, inducing large pressure gradients, on a premixed turbulent flame is studied using direct numerical simulations. A favourable pressure gradient, i.e. a pressure decrease from unburnt to burnt gases, is found to decrease the flame wrinkling, the flame brush thickness, and the turbulent flame speed. It also promotes counter-gradient turbulent transport. On the other hand, adverse pressure gradients tend to increase the flame brush thickness and turbulent flame speed, and promote classical gradient turbulent transport. As proposed by Libby (1989), the turbulent flame speed is modified by a buoyancy term linearly dependent on both the imposed pressure gradient and the integral length scale l t . A simple model for the turbulent flux uc is also proposed, validated from simulation data and compared to existing models. It is shown that turbulent premixed flames can exhibit both gradient and counter-gradient transport and a criterion integrating the effects of pressure gradients is derived to differentiate between these regimes. In fact, counter-gradient diffusion may occur in most practical ducted flames.
A chiral triaminosulfonium salt: design and application to catalytic asymmetric synthesis

Abstract The first chiral triaminosulfonium salt, tris(( S,S )-3,4-diphenylpyrrolidino)sulfonium difluorotriphenylstannate, catalyzes trifluoromethylation of benzaldehyde with (trifluoromethyl)trimethylsilane to give the corresponding optically active alcohol with 52% ee.
Hydrodynamic stability and frames of reference

The dependence of criteria of hydrodynamic stability upon a frame of reference is discussed. It is demonstrated that these criteria are not frame indifferent.
Self-Consistent Cluster Theory of Disordered Alloys

Several techniques for extending the single-site coherent-potential approximation (CPA) to account for particular local configurations of atoms are evaluated. It is shown that if one attempts to define a site-diagonal medium by requiring consistency between the Green's function evaluated at the center of the cluster and the external medium, one may obtain unphysical results. If, however, one requires consistency between a site at the boundary and the medium, one can obtain (at least in one dimension) a site-diagonal medium which reproduces the cellular CPA exactly.
An efficient synthetic route to 2-(1,2-dithiolan-3-yl)acetic acid. Trisnorlipoic acid and amide derivatives

Abstract A simple, efficient synthesis of 2-(1,2-dithiolan-3-yl)acetic acid from Meldrum's acid, acrolein and thioacetic acid is described. The isopropyldene 2,4- bis (acetylthio)butane-1,1-dicarboxylate formed in the three-component, single container process, can be methanolized to the corresponding dimethyl ester and then hydrolyzed, oxidized to the disulfide and decarboxylated to 2-(1,2-dithiolan-3-yl)acetic acid. The acid can be converted by conventional reagents into a variety of amide derivatives.
String orbifolds and quotient stacks

Abstract In this note we observe that, contrary to the usual lore, string orbifolds do not describe strings on quotient spaces, but rather seem to describe strings on objects called quotient stacks, a result that follows from simply unraveling definitions, and is further justified by a number of results. Quotient stacks are very closely related to quotient spaces; for example, when the orbifold group acts freely, the quotient space and the quotient stack are homeomorphic. We explain how sigma models on quotient stacks naturally have twisted sectors, and why a sigma model on a quotient stack would be a nonsingular CFT even when the associated quotient space is singular. We also show how to understand twist fields in this language, and outline the derivation of the orbifold Euler characteristic purely in terms of stacks. We also outline why there is a sense in which one naturally finds B ≠0 on exceptional divisors of resolutions. These insights are not limited to merely understanding existing string orbifolds: we also point out how this technology enables us to understand orbifolds in M-theory, as well as how this means that string orbifolds provide the first example of an entirely new class of string compactifications. As quotient stacks are not a staple of the physics literature, we include a lengthy tutorial on quotient stacks, describing how one can perform differential geometry on stacks.
JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems

In the last few years a significant population of ultracool L and T dwarfs has been discovered. With effective temperatures ranging from ~2200 to 700 K, these objects emit most of their radiation in the near-IR, and their spectral energy distributions are dominated by strong molecular absorption bands. These highly structured energy distributions lead to JHK magnitudes that are extremely sensitive to the exact filter bandpass used. In the case of the T dwarfs, the differences between commonly used photometric systems can be as large as 0.4 mag at J and 0.5 mag at J–K. Near-IR magnitudes have been published for L and T dwarfs using a variety of photometric systems. Currently, the data obtained with these systems cannot be accurately compared or combined, as transformations based on the colors of hotter stars are not valid for L and T dwarfs. To address this problem, we have synthesized J, H, and K magnitudes for some of the common photometric systems and present transformation equations with respect to the most atmospheric-independent system, the Mauna Kea Observatory filter set. If the spectral type of the dwarf is known, our transformations allow data to be converted between systems to 0.01 mag, which is better than the typical measurement uncertainty. Transforming on the basis of color alone is more difficult because of the degeneracy and intrinsic scatter in the near-IR colors of L and T dwarfs; in this case J magnitudes can only be transformed to 0.05 mag and H and K to 0.02 mag.
The relation between earnings and cash flows

Abstract A model of earnings, cash flows and accruals is developed assuming a random walk sales process, variable and fixed costs, and that the only accruals are accounts receivable and payable, and inventory. The model implies earnings better predict future operating cash flows than current operating cash flows and the difference varies with the operating cash cycle. Also, the model is used to predict serial and cross-correlations of each firm's series. The implications and predictions are tested on a 1337 firm sample over 1963–1992. Both earnings and cash flow forecast implications and correlation predictions are generally consistent with the data.
Changes in REIT Liquidity 1988–2007: Evidence from Daily Data

In this study, we present panel-data evidence on REIT liquidity and its determinants over the 1988–2007 period. We focus upon liquidity measures that do not require micro-structure data (1) to facilitate use of our results as benchmarks for comparisons with results from international markets for which micro-structure data may be unavailable, (2) to provide benchmarks that do not require access to costly (and voluminous) micro-structure data. We find that REIT liquidity improved during the early and mid-1990s, deteriorated during the late 1990s, and then improved dramatically during 2000–2006, with the notable exception of 2007. Liquidity improved the most for REITs traded on the NYSE, and was an order of magnitude better than liquidity of REITs traded on the AMEX or NASDAQ. We link the deterioration in liquidity observed in 2007 to the investment portfolio of a REIT. We find that the percentage bid-ask spread is highly correlated with the measure of price impact proposed by Amihud (2002). We provide panel-data evidence on the key determinants of the percentage bid-ask spread that largely confirms the results reported by Bhasin et al. (1997) for 1990 and 1994: the percentage spread is a positive function of the volatility of stock returns, and a negative function of dollar volume turnover, share price and market capitalization. Finally, we provide evidence that these results obtained using daily closing bid- and ask-prices are not qualitatively different from those obtained using market micro-structure data. This suggests that we can use liquidity measures based upon readily available daily return data rather than being forced to rely upon market micro-structure data.
Thermally and molecularly stimulated relaxation of hot phonons in suspended carbon nanotubes

The high-bias electrical transport properties of suspended metallic single-walled carbon nanotubes (SWNTs) are investigated at various temperatures in vacuum, in various gases, and when coated with molecular solids. It is revealed that nonequilibrium optical phonon effects in suspended nanotubes decrease as the ambient temperature increases. Gas molecules surrounding suspended SWNTs assist the relaxation of hot phonons and afford enhanced current flow along nanotubes. Molecular solids of carbon dioxide frozen onto suspended SWNTs quench the nonequilibrium phonon effect. The discovery of strong environmental effects on high current transport in nanotubes is important to high performance nanoelectronics applications of 1D nanowires in general.
Swift XRT Observations of the Possible Dark Galaxy VIRGOHI 21

Swift XRT observations of the H I line source VIRGOHI 21 were performed on 2008 April 22 and 26 for a total exposure time of 9.2 ks. This is the first pointed X-ray observation of VIRGOHI 21, a putative dark galaxy in the Virgo Cluster, and no photons were detected from this source. The nondetection of extended X-ray emission within the angular extent of the H I source corresponds to a 99% confidence upper limit of -->2.1 × 10−14 ergs cm -->−2 s -->−1 in the 0.3-2.0 keV band. The equivalent upper limit to the amount of diffuse hot gas associated with VIRGOHI 21 is in the range 4 × 107-2 × 108 -->M☉ for a hot gas temperature between 0.1 and 1 keV. The nondetection also corresponds to a 99% confidence upper limit on the flux from a pointlike source of -->8 × 10−15 ergs cm -->−2 s -->−1 in the 0.3-2.0 keV band. We discuss the constraints on the nature of VIRGOHI 21 imposed by these observations and the theoretical implications of these results.
A Predictably Selective Aliphatic C-H Oxidation Reaction for Complex Molecule Synthesis

Realizing the extraordinary potential of unactivated sp3 C–H bond oxidation in organic synthesis requires the discovery of catalysts that are both highly reactive and predictably selective. We report an iron (Fe)–based small molecule catalyst that uses hydrogen peroxide (H2O2) to oxidize a broad range of substrates. Predictable selectivity is achieved solely on the basis of the electronic and steric properties of the C–H bonds, without the need for directing groups. Additionally, carboxylate directing groups may be used to furnish five-membered ring lactone products. We demonstrate that these three modes of selectivity enable the predictable oxidation of complex natural products and their derivatives at specific C–H bonds with preparatively useful yields. This type of general and predictable reactivity stands to enable aliphatic C–H oxidation as a method for streamlining complex molecule synthesis.
Acceleration Effects on the Cooling Performance of a Partially Confined FC-72 Spray

This paper discusses the effects of a variable-gravity environment on the performance of a subcooled partially confined spray. An experiment consisting of a test chamber, associated flow loops, and instrumentation was fabricated and flown on the NASA Reduced-Gravity Testing Platform. This modified KC-135 aircraft followed a parabolic flight path to provide various acceleration levels. The spray chamber contained a nozzle spraying onto an upward-facing thick-film resistor heater, which was mounted on an insulating glass pedestal. Thermocouples under the heater in the glass pedestal were used to determine the heater surface temperature. The glass pedestal was surrounded by an annular sump system, which was used to collect and remove the cooling fluid from the test chamber. The fluid used for this testing was FC-72, which is a nontoxic, nonflammable, and nonreactive refrigerant. Because of its dielectric nature, FC-72 was sprayed directly onto the thick-film heater. The parametric ranges of this experiment were as follows: heat flux to the spray was 21.1 ≤ q" sp ≤ 69.0 W/cm 2 , acceleration field was 0.15 ≤ a ≤ 1.80 g, coolant volumetric flow rate was 6.18 ≤ V ≤ 8.94 ml/s, and coolant subcooling was 23.1 ≤ Δ T sc ≤ 31.7 K. The heat fluxes tested were below the critical heat flux q" CHF . The wall superheat ΔT sat = T s - T sat was found to increase with heat input and acceleration and to decrease with subcooling and volumetric flow rate.
The preparation of 3-chloroalkenoyltrimethylsilanes

Abstract 3,3-Dichloropropenoyltrimethylsilane undergoes monosubstitution with organocuprates RCu(CN)Li to afford E -3-chloroalkenoyltrimethylsilanes.
Waveform-diverse moving-target spotlight SAR

This paper develops the theory for waveform-diverse moving-target synthetic-aperture radar. We assume that the targets are moving linearly, but we allow an arbitrary flight path and (almost) arbitrary waveforms. We consider the monostatic case, in which a single antenna phase center is used for both transmitting and receiving. This work addresses the use of waveforms whose duration is sufficiently long that the targets and/or platform move appreciably while the data is being collected.
Limitations of B-meson mixing bounds on technicolor theories

Abstract Recent work by Burdman, Lane, and Rador has shown that B B mixing places stringent lower bounds on the masses of topgluons and Z′ bosons in classic topcolor-assisted technicolor (TC2) models. This Letter finds analogous limits on the Z′ bosons of flavor-universal TC2 and non-commuting extended technicolor models, and compares the limits with those from precision electroweak measurements. A discussion of the flavor structure of these models (contrasted with that of classic TC2) shows that B-meson mixing is a less reliable probe of these models than of classic TC2.
Squaraine dyes in molecular recognition and self-assembly

Squaraine dye molecules and their derivatives are gaining significant interest in the field of supramolecular chemistry, both in host–guest recognition and self-assembly. The unique structure and properties of squaraine molecules has led to extensive research into their use as sensors. This feature article covers the most recent studies (2004–2009) in the development, characterization, and application of squaraine dye-based molecular sensors, self-assembly, and their use in polymeric materials and biological applications.
Nucleophilic Substitution Reactions of 5-Bromo-6-methyluridines

Abstract The reactions of the 5-bromo-6-methyl-2′,3′-O-isopropylideneuridines 9 and 10 with a number of nucleophiles in hot DMF have been investigated. With acetate ion as the nucleophile, either the 5-acetoxy- (11,12) or the 6-acetoxymethyl- (15) products can be obtained in modest yield depending upon the exact reaction conditions. With nitrogen nucleophiles (aniline or p-methoxybenzylamine) reaction takes place at the 6-methyl carbon, whereas with sulfur nucleophiles (thiophenol, thioacetate) only the 5-substituted products are obtained.
Failure modes in vapor‐deposited organic led's

A study of the main failure mechanisms in vacuum vapor-deposited organic light-emitting diodes (LED's) is presented. Three degradation modes were identified for a prototype bilayer ITO/TPD/Alq 3 /Mg/Ag device: a) formation and growth of black non-emissive spots, b) abrupt ceasing of light emission associated with catastrophic failures caused by electrical shorts, and c) long term wearout associated with the decrease of quantum efficiency and luminance along with an increase in voltage, while the device is stressed under constant current.
Supraceliac Aortorenal Bypass

Abstract Purpose: To determine the efficacy and durability of supraceliac aortorenal bypass grafting for symptomatic atherosclerotic renal artery disease. Methods: Retrospective review of a 10-year, single-institution experience. Results: Seventeen patients underwent 27 bypass procedures (seven unilateral, 10 bilateral) for atherosclerotic renovascular hypertension. The patients' mean age was 62.7 ± 8.8 years. Diffuse aortoiliac and visceral atherosclerosis was confirmed on arteriogram; most (88%) celiac axis branches and all infrarenal aortas and common iliac arteries were found unsuitable for use as a donor vessel. Twenty-six bypass procedures (96%) were performed with autologous vein grafts. Seventeen bypass procedures (63%) were performed during partial aortic occlusion. There were no operative deaths or early occlusions. Postoperative complications occurred in four patients (24%). The mean duration of follow-up was 28 ± 19 months (range, 2 to 69 months). By life table analysis, the 5-year primary patency and assisted primary patency rates were 95% and 100%, respectively. The mean systolic blood pressure decreased from 180 ± 38 mm Hg to 135 ± 20 mm Hg ( p = 0.0003), and the mean diastolic blood pressure decreased from 96 ± 16 mm Hg to 77 ± 9 mm Hg ( p = 0.0002). The number of antihypertensive medications decreased from 2.8 ± 1.2 to 1.4 ± 1.0 ( p = 0.002). Significant improvement in serum creatinine level was seen among patients with preoperative renal insufficiency. Hypertension was cured in 29%, improved in 53%, and unchanged in 18%. During late follow-up, only four patients (24%) required subsequent aortic reconstruction. Conclusion: Supraceliac aortorenal bypass grafting is a safe and durable alternative for renal artery revascularization. This technique should be considered in patients who have diffuse infrarenal aortoiliac and visceral artery occlusive disease and require renal revascularization procedures.
A theory for stress analysis of composite laminates

Failures in laminated resin matrix composite materials often begin with matrix microcracking and delamination. These modes of damage are three-dimensional in nature and are controlled by interlaminar stresses. One important key to understanding and ultimately predicting the failures in composite materials is an analytical approach that provides reliable stress estimates in critical regions. Conventional laminate theories are inadequate for this purpose as they are based on global displacement assumptions. Moreover, the interlaminar stresses are often neglected in the initial formulations. Therefore, solutions based upon these theories cannot yield realistic stress distributions. Recent theoretical research shows that there are certain nonclassical influences that affect bending-related behavior. They include section warping and its concomitant nonclassical surface-parallel stress contributions and transverse normal strain. The stress prediction capability of a bending theory improves significantly if these nonclassical influences are incorporated. A comprehensive bending theory is developed for arbitrary composite laminates. Its effectiveness is demonstrated in examples for a cross-ply laminate and a quasiisotropic laminate.
The Artin conjecture for some $$S_5$$ -extensions

We establish some new cases of Artin’s conjecture. Our results apply to Galois representations over $$\mathbf{Q }$$ with image $$S_5$$ satisfying certain local hypotheses, the most important of which is that complex conjugation is conjugate to $$(12)(34)$$ . In fact, we prove the stronger claim conjectured by Langlands that these representations are automorphic. For the irreducible representations of dimensions 4 and 6, our result follows from known 2-dimensional cases of Artin’s conjecture (proved by Sasaki) as well as the functorial properties of the Asai transfer proved by Ramakrishnan. For the irreducible representations of dimension 5, we encounter the problem of descending an automorphic form from a quadratic extension compatibly with the Galois representation. This problem is partly solved by working instead with a four dimensional representation of some central extension of $$S_5$$ . Our modularity results in this case are contingent on the non-vanishing of a certain Dedekind zeta function on the real line in the critical strip. A result of Booker show that one can (in principle) explicitly verify this non-vanishing, and with Booker’s help we give an example, verifying Artin’s conjecture for representations coming from the (Galois closure) of the quintic field $$K$$ of smallest discriminant (1609).
A Parallel Version of the Fast Multipole Method

Abstract This paper presents a parallel version of the fast multipole method (FMM). The FMM is a recently developed scheme for the evaluation of the potential and force fields in systems of particles whose interactions are Coulombic or gravitational in nature. The sequential method requires O(N) operations to obtain the fields due to N charges, rather than the O(N2) operations required by the direct calculation. Here, we describe the modifications necessary for implementation of the method on parallel architectures and show that the expected time requirements grow as log N when using N processors. Numerical results are given for a shared memory machine (the Encore Multimax 320).
Regularity for the Supercritical Fractional Laplacian with Drift

We consider the linear stationary equation defined by the fractional Laplacian with drift. In the supercritical case, wherein the dominant term is given by the drift instead of the diffusion component, we prove local regularity of solutions in Sobolev spaces employing tools from the theory of pseudo-differential operators. The regularity of solutions in the supercritical case is as expected from the subcritical case. In the subcritical case the diffusion is at least as strong as the drift, and the operator is an elliptic pseudo-differential operator, which is not the case in the supercritical regime. We also compute the leading part of the singularity of the Green’s kernel for the supercritical case, which displays some rather unusual behavior.
Mechanical properties of pyrolytic graphite

Abstract : A series of mechanical strength and thermal expansion tests was carried out from room temperature to 5000 F on the two microstructural types of current production pyrolytic graphite. Results indicate that with appropriate precautions in selecting test material, machining and testing specimens, current production pyrolytic graphites yield higher, more reliable mechanical property values. The contribution of process improvements to this increase cannot be specifically separated although it may show up principally in allowing more of a given batch of material to be selected. The present series of tests shows pyrolytic graphite to have an ultimate 'a' direction tensile strength of 18,000 = 2,000 psi at room temperature rather than previously found values of 11,000 = 5,000 psi. The largest difference between surface nucleated and continuously nucleated material was obtained in torsional tests parallel to the planes; values of 1555 = 60 and 2880 = 265 psi were obtained respectively throughout the temperature range to 5000 F.
An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst

We present a synthetic spectral analysis of nearly the entire far-ultraviolet International Ultraviolet Explorer (IUE) archive of spectra of dwarf novae in or near outburst. The study includes 46 systems of all dwarf nova subtypes, both above and below the period gap. The spectra were uniformly analyzed using synthetic spectral codes for optically thick accretion disks and stellar photospheres, along with the best available distance measurements or estimates. We present newly estimated accretion rates and discuss the implications of our study for disk accretion physics and CV evolution.
Infiltration of Porous Alumina Bodies with Solution Precursors: Strengthening via Compositional Grading, Grain Size Control, and Transformation Toughening

Alumina powder compacts, partially densified with a lowtemperature heat treatment and then cut into bars, were infiltrated with liquid precursors that decomposed to either mullite (3Al2O3·2SiO2), fully stabilized zirconia (cubic Zr(8Y)O2), or partially stabilized zirconia (tetragonal Zr(4Y)O2). The specimens were repeatedly infiltrated and pyrolyzed to achieve a higher concentration of the precursor near the surface. The infiltrated bodies were then densified at 1500°C/2 h. Residual stresses developed during cooling from the densification temperature because of the higher concentration of the second phase near the surface and their differential thermal expansion relative to the matrix material. At least 10 bars of each two-phase material were fractured in four-point bending to determine the effect of the second phase on strength. The alumina bars without a second phase had a larger grain size (∼7 μm) and a mean strength of 253 MPa. The intruded phases significantly reduced the Al2O3 grain size to ∼1 1μm. Despite their higher concentration near the surface and apparent surface tensile stress, both of the Zr(Y)O2 phases increased the mean strength to 413 MPa (c-Zr(8Y)O2) and 582 MPa (t-Zr(4Y)O2, an apparent toughening agent). The mullite second phase produced a high mean strength of 588 MPa, apparently due to its concentration gradient creating a compressive surface stress.
Preparation of bis and tris(arylimido) complexes of rhenium(VII), including bis(arylimido) neopentylidene complexes, candidates as olefin metathesis catalysts

Abstract The reaction between ReO3(OSiMe3) and 3 equiv. of ArNCO (Ar = 2,6-C6H3iPr2) yields mixtures of (ArN)3ReORe(O)(NAr)2 (1), Re(O)(NAr)3(OSiMe3) (2a), and what is proposed to be Re(O)(NAr)2(OSiMe3) (3). Conditions can be altered in order to yield 1 or 2a in satisfactory yield, but 3 has not been prepared in pure form. Analogous reactions between ReO3(OSiMe3) and 3 equiv. of Ar′NCO (Ar′ = 2,6-C6H3Me2) yield (Ar′N)3ReORe(NAr′)3 (4) and Re(NAr′)3(OSiMe3) (2b), while those between ReO3(OSiMe3) and 3 equiv. of Ar″NCO (Ar″ = 2,6-C6H3Cl2) yield only Re(NAr″)3(OSiMe3) (2c). Complexes of the type Re(NR)3(CH2tBu) (R = Ar, Ar′, Ar″) have been prepared straightforwardly. Complexes of the type Re(NR)2Cl3(py) (6) can be prepared by treating tris(imido) complexes 2 with 3 equiv. of pyHCl. These can be alkylated to give mononeopentyl bis(imido) derivatives, Re(NR)2(CH2tBu)Cl2 (8), in high yield. Dehydrohalogenation of Re(NAr)2 (CH2tBu)Cl2 yields Re(NAr)2(CHtBu)Cl, from which several monoalkoxide derivatives have been prepared (OR = OCH(CF3)2, OCMe(CF3)2, or O-2,6-C6H3tPr2). Dehydrohalogenation of Re(NAr′)2(CH2tBu)Cl2 or Re(NAr″)2(CH2tBu)Cl2 did not yield neopentylidene complexes analogous to Re(NAr)2(CHtBu)Cl2. None of the neopentylidene complexes showed any well-defined metathesis activity, even with norbornene.
The Joule-Thomson effect for air at moderate temperatures and pressures

Synopsis.---In the experiments as described air was pumped first through a set of tubes designed to remove carbon dioxide and moisture, then through the throttling device or "porous plug" and finally back to the pump. The plug and tubing immediately leading to it were immersed in an oil bath thermostat. The bath temperatures, for the most part, lay between 0\ifmmode^\circ\else\textdegree\fi{} and 100\ifmmode^\circ\else\textdegree\fi{} C., the mean pressures, from 4.5 to 6.4 meters of mercury, while the pressure-drop varied between 0.25 and 0.80 meters of mercury. The temperature-drop was measured by platinum resistance thermometers differentially connected. The plug was of the radial flow type originated by Regnault, roughly cylindrical in form, through the walls of which the air flowed toward the axis, escaping finally through one end. The accidental errors were apparently of an order under one per cent.
Tomography of Massive Stars from Core Collapse to Supernova Shock Breakout

Neutrinos and gravitational waves are the only direct probes of the inner dynamics of a stellar core collapse. They are also the first signals to arrive from a supernova (SN) and, if detected, establish the moment when the shock wave is formed that unbinds the stellar envelope and later initiates the optical display upon reaching the stellar surface with a burst of UV and X-ray photons, the shock breakout (SBO). We discuss how neutrino observations can be used to trigger searches to detect the elusive SBO event. Observation of the SBO would provide several important constraints on progenitor structure and the explosion, including the shock propagation time (the duration between the neutrino burst and SBO), an observable that is important in distinguishing progenitor types. Our estimates suggest that next-generation neutrino detectors could exploit the overdensity of nearby SNe to provide several such triggers per decade, more than an order-of-magnitude improvement over the present.
Constraints on the Inner Mass Profiles of Lensing Galaxies from Missing Odd Images

Most gravitational lens systems consist of two or four observable images. The absence of detectable odd images allows us to place a lower limit on the power-law slope of the inner mass profile of lensing galaxies. Using a sample of six two-image radio-loud lens systems and assuming a singular power-law surface density (Σ ∝ r-β) for the inner several kiloparsecs of the mass distribution, we find that there is less than a 10% probability that the data are consistent with profile slopes β 0.85 for B0739+366 and β > 0.91 for B1030+074. Modeling central black holes as additional point masses changes the constraints in these systems to β > 0.84 and β > 0.83, respectively. The inner mass profiles of lensing galaxies are therefore not much shallower than isothermal.
THE TIDAL DISRUPTION OF GIANT STARS AND THEIR CONTRIBUTION TO THE FLARING SUPERMASSIVE BLACK HOLE POPULATION

Sun-like stars are thought to be regularly disrupted by supermassive black holes (SMBHs) within galactic nuclei. Yet, as stars evolve off the main sequence their vulnerability to tidal disruption increases drastically as they develop a bifurcated structure consisting of a dense core and a tenuous envelope. Here we present the first hydrodynamic simulations of the tidal disruption of giant stars and show that the core has a substantial influence on the star's ability to survive the encounter. Stars with more massive cores retain large fractions of their envelope mass, even in deep encounters. Accretion flares resulting from the disruption of giant stars should last for tens to hundreds of years. Their characteristic signature in transient searches would not be the t –5/3 decay typically associated with tidal disruption events, but a correlated rise over many orders of magnitude in brightness on timescales of months to years. We calculate the relative disruption rates of stars of varying evolutionary stages in typical galactic centers, then use our results to produce Monte Carlo realizations of the expected flaring event populations. We find that the demographics of tidal disruption flares are strongly dependent on both stellar and black hole mass, especially near the limiting SMBH mass scale of ~108 M ☉. At this black hole mass, we predict a sharp transition in the SMBH flaring diet beyond which all observable disruptions arise from evolved stars, accompanied by a dramatic cutoff in the overall tidal disruption flaring rate. Black holes less massive than this limiting mass scale will show observable flares from both main-sequence and evolved stars, with giants contributing up to 10% of the event rate. The relative fractions of stars disrupted at different evolutionary states can constrain the properties and distributions of stars in galactic nuclei other than our own.
Utilization of core wash material in the diagnosis of breast lesions by stereotactic needle biopsy.

BACKGROUND Several reports have compared the results of fine-needle aspiration and stereotactic core needle biopsy in nonpalpable breast lesions. In this study the authors describe a simple method to retrieve cytologic material from a core breast biopsy sample that provides the diagnosis within 1 hour of the procedure. METHODS Two hundred and eleven nonpalpable breast lesions were biopsied. Each core needle biopsy sample was placed in a mesh bag, and the bag and needle notch were washed in CytolytR solution to obtain a monolayer using a commercial ThinPrepR processor. The cytologic diagnoses were divided into four categories: benign, suspicious, malignant, and unsatisfactory, which then were compared with core needle biopsy results. RESULTS Cytology reports of 211 lesions were as follows: 169 lesions (80%) were benign, 16 lesions (7.6%) were suspicious, 11 lesions (5.2%) were malignant, and 15 lesions (7.1%) were unsatisfactory. Core needle biopsy showed 165 of 169 samples (98%) to be benign and 4 to be malignant. Of the 16 suspicious smears, 10 were invasive carcinoma, 2 were in situ lesions, 3 were hyperplasias, and 1 was fibrosis. Of the 11 malignant smears, 10 were confirmed on core needle biopsy and 1 was read as atypia on the first core needle biopsy sample and malignant on a second, separate, follow-up core needle biopsy. Of the 15 unsatisfactory samples, 14 were found to be benign and 1 was found to be malignant on a separate, follow-up core needle biopsy. CONCLUSIONS The core wash technique was 85% sensitive and 98% specific for malignancy. Only 7% of specimens were insufficient for diagnosis, and 93% of these were proven to be benign. This technique is useful for immediate (within 1 hour) diagnosis of breast lesions, alleviating patient anxiety and supplementing the diagnostic yield of the core biopsy. Cancer (Cancer Cytopathol) 1998;84:98-100. © 1998 American Cancer Society.
Microwave synthesis of Au–Rh core–shell nanoparticles and implications of the shell thickness in hydrogenation catalysis

A microwave-assisted heating method allows for the convenient and reproducible synthesis of defined Au–Rh core–shell metallic nanoparticles with tuneable shell thicknesses. Nanoparticles with shells as thin as two Rh monolayers can be prepared, which are effective in vapour-phase hydrogenation catalysis at room temperature without the need for pre-treatment. Particles with Rh shells consisting of two or four Rh overlayers show similar catalytic properties and are both significantly more highly active than pure Rh nanoparticles, per mol of Rh employed.
Algebraic characterization of X-states in quantum information

A class of two-qubit states called X-states are increasingly being used to discuss entanglement and other quantum correlations in the field of quantum information. Maximally entangled Bell states and 'Werner' states are subsets of them. Apart from being so named because their density matrix looks like the letter X, there is not as yet any characterization of them. The su(2) × su(2) × u(1) subalgebra of the full su(4) algebra of two qubits is pointed out as the underlying invariance of this class of states. X-states are a seven-parameter family associated with this subalgebra of seven operators. This recognition provides a route to preparing such states and also a convenient algebraic procedure for analytically calculating their properties. At the same time, it points to other groups of seven-parameter states that, while not at first sight appearing similar, are also invariant under the same subalgebra. And it opens the way to analyzing invariant states of other subalgebras in bipartite systems.
Guidance analysis of the multiple outer-planet /grand-tour/ mission.

Spacecraft guidance analysis of multiple outer planet mission utilizing gravity assist swingbys to achieve planetary flybys with single spacecraft
Effect of localized electric fields on the evolution of the velocity distribution function

The interaction between charged particles and sharply localized fields is investigated. The random particle scattering is described by a Fokker-Planck equation whose time-dependent solution exhibits the formation of a highly populated superthermal tail.
A Laser Technology Test Facility for Laser Inertial Fusion Energy (LIFE)

A LIFE laser driver needs to be designed and operated which meets the rigorous requirements of the NIF laser system while operating at high average power, and operate for a lifetime of >30 years. Ignition on NIF will serve to demonstrate laser driver functionality, operation of the Mercury laser system at LLNL demonstrates the ability of a diode-pumped solid-state laser to run at high average power, but the operational lifetime >30 yrs remains to be proven. A Laser Technology test Facility (LTF) has been designed to specifically address this issue. The LTF is a 100-Hz diode-pumped solid-state laser system intended for accelerated testing of the diodes, gain media, optics, frequency converters and final optics, providing system statistics for billion shot class tests. These statistics will be utilized for material and technology development as well as economic and reliability models for LIFE laser drivers.
Thiol-ene chemistry of vinylsilanes

The thiol-ene addition reaction is a clean, effective method for the introduction of the thioether functionality into unsaturated compounds. Though widely used in organic, polymer and materials chemistry, the application of the thiol-ene reaction in organosilicon chemistry has been relatively minimal. The literature discussed here emphasizes the synthetic utility of thiol-ene reactions of vinylsilanes by highlighting the following areas: (1) the tolerance of various vinylsilane derivatives, (2) the reactivity of various substituents on the vinylsilane moiety, (3) the simplicity of reaction conditions, and (4) the versatility of reaction products as intermediates.
String model building in the age of D-Branes

The string duality revolution calls into question virtually all of the working assumptions of string model builders. A number of difficult questions arise. I use fractional charge as an example of a criterion which one would hope is robust beyond the weak coupling heterotic limit.
The Near Infrared Camera on the W.M. Keck Telescope

The near infrared camera (NIRC) was used for a science demonstration run on the Keck telescope during 16–24 March 1993. The camera used a 256 x 256 InSb array manufactured by Santa Barbara Research Corporation. Observations were obtained using narrowband and broad band filters from 1 to 2.4 microns, and grisms with a spectral resolution of 0.6 percent in the J, H and K atmospheric windows. The instrument was fully background limited over the entire wavelength range. The sky background was quite low, reaching 14.3 mag/square arc sec in the broadband K s filter. The image quality of the camera + telescope was excellent, being seeing limited in the range 0.5″-0.9″.
The Synthesis and Crystal Structure of NpSe3

Neptunium triselenide, NpSe3, was synthesized in high yield by the reaction of the elements in a Sb2Se3 flux at 1223 K. Its structure has been determined by single-crystal X-ray diffraction methods. The compound crystallizes with two formula units in space group C 2-P21/m of the monoclinic system in the TiS3 structure type with cell constants at 100 K of a = 5.592(3) A, b = 4.002(2) A, c = 9.422(5) A,
Formation of Short-Period Binary Pulsars in Globular Clusters.

We present a new dynamical scenario for the formation of short-period binary millisecond pulsars in globular clusters. Our work is motivated by the recent observations of 20 radio pulsars in 47 Tuc. In a dense cluster such as 47 Tuc, most neutron stars acquire binary companions through exchange interactions with primordial binaries. The resulting systems have semimajor axes in the range ~0.1-1 AU and neutron star companion masses ~1-3 M☉. For many of these systems, we find that when the companion evolves off the main sequence and fills its Roche lobe, the subsequent mass transfer is dynamically unstable. This leads to a common envelope phase and the formation of short-period neutron star-white dwarf binaries. For a significant fraction of these binaries, the decay of the orbit due to gravitational radiation will be followed by a period of stable mass transfer driven by a combination of gravitational radiation and tidal heating of the companion. The properties of the resulting short-period binaries match well those of observed binary pulsars in 47 Tuc.