cssi/SciSciGPT-SciSciNet huggingface dataset:
On the Hardness of Approximating Stopping and Trapping Sets in LDPC Codes

We prove that approximating the size of the smallest trapping set in Tanner graphs of linear block codes, and more restrictively, LDPC codes, is NP-hard. The proof techniques rely on reductions from three NP-hard problems, the set cover, minimum three-dimensional matching, and the minimum Hamming distance problem. The ramifications of our findings are that methods used for estimating the height of the error-floor of long LDPC codes, centered around trapping set enumeration, cannot provide accurate worst-case performance predictions.
Adequate Failure Analysis When Life Testing Electronic Equipment

Careful and diligent failure analysis is necessary to obtain maximum benefit from life tests of electronic equipments. The importance of good failure analysis is often underrated in a test program, to the detriment of the program. This paper discusses the role and the significance of correct attitudes, advance indoctrination, thorough planning, skills, facilities, and effective supervision in adequately diagnosing each failure incident, in recording its details, and in preserving the lesson learned.
Latissimus dorsi myocutaneous flap for secondary head and neck reconstruction.

Abstract Purpose: To review our experience and results with the use of pedicled latissimus dorsi myocutaneous flap (LDMF) for secondary reconstruction in head and neck surgery. Methods: Twenty-two patients had LDMF, 17 of them for secondary reconstruction. Data were collected regarding the primary surgery, primary method of reconstruction, indication for secondary reconstruction, and outcome. Results: Seventeen LDMF procedures were performed for secondary reconstruction. Flap success rate was 100%. Reconstructive goals were achieved immediately in 16 (94.1%) patients. Conclusion: LDMF is a thin flap with a large surface area and a long pedicle that allows it to reach any region in the head, neck, and scalp. Its main disadvantages are the need for lateral positioning of the patient and the fact that its pedicle is not protected with muscle. In our experience, LDMF provides an excellent reconstructive option especially in complicated cases of secondary reconstruction. It may be used in cases where a free flap is usually used, but with significantly reduced surgical time.
Directional ground-fault indicator for high-resistance grounded systems

Locating ground faults is a difficult and challenging problem for low-voltage power systems that are ungrounded or have high-impedance grounding. Recent work in pilot signals has renewed efforts in developing fault location methodologies. This paper presents a method for directional ground-fault indication that utilizes the fundamental frequency voltages and currents. Although the ground-fault current is small and usually less than the load currents, the fault has zero-sequence components that distinguish it from the load. Signal processing techniques are used to identify and compare the fault signals to determine the fault direction. The process takes advantage of the currents flowing from the distributed grounding capacitance. An experimental microprocessor-based directional indicator unit is tested in an industrial power distribution system. Directional indication of ground faults is applied near tap-off branch circuit connections. Promising results from field test conducted in a harmonic-noisy setting are presented. Directional indicator units simplify the search process on large networks, thus reducing the time and effort necessary to locate and remove the fault, and thereby significantly reduces the probability of a second ground fault with its destructive currents.
To share or not to share: Does local participation matter for spillovers from foreign direct investment? ☆

This study examines whether the degree of spillovers from foreign direct investment is affected by the foreign ownership share in investment projects. The analysis, based on an unbalanced panel of Romanian firms during 1998-2000, produces evidence consistent with positive intra-sectoral spillovers resulting from fully-owned foreign affiliates but not from projects with joint domestic and foreign ownership. This finding is in line with the literature suggesting that foreign investors tend to put more resources into technology transfer to their wholly-owned projects than to those owned partially. Further, the data indicate that the presence of partially foreign-owned projects is correlated with higher productivity of domestic firms in upstream industries suggesting that domestic suppliers benefit from contacts with multinational customers. The opposite is true, however, in the case of fully-owned foreign affiliates which appear to have a negative effect on domestic firms in upstream industries. These results are consistent with the observation that foreign investors entering a host country through greenfield projects are less likely to source locally than those engaged in joint ventures or partial acquisitions. They are also in line with the evidence suggesting that fully-owned foreign subsidiaries use newer or more sophisticated technologies than jointly owned investment projects and thus may have higher requirements vis-a-vis suppliers.
Experiments in the recognition of hand-printed text, part II: context analysis

The work described in this paper is part of a larger effort aimed at the recognition of hand-printed text. In a companion paper, Munson describes the scanning of the text, and the preprocessing and tentative classification of individual characters. In this paper, we describe techniques for using context to detect and correct errors in classification.
Kinetics of high-temperature spreading

Abstract This paper reviews the recent advances in the experimental and theoretical analysis of the high-temperature spreading of molten metals and oxides. Results obtained in the analysis of simple non-reactive systems are compared with current theories developed for room-temperature liquids. These results outline the critical role in spreading at high-temperature of the local dissipation at the triple solid–liquid–vapor junction. However, in most high-temperature systems, the substrate cannot be described as an ideal solid – rigid and insoluble – and the movement of the triple junctions is accompanied by other phenomena such as ridging, interdiffusion, and chemical reactions (reactive spreading). The effect of these phenomena is outlined and a framework for the theoretical analysis of reactive spreading emerges. This framework is based on the division of the reactive spreading process into its constituent steps, and the identification of the step that drives spreading and controls its kinetics. A key aspect of the analysis is the description of the structure of the triple junction and the identification of the relative kinetics of the movement of the liquid and the other phenomena that accompany spreading.
Self to Self

At the end of "The Imagination and the Self," Bernard Williams uncovers a common confusion about the range of thoughts in which the metaphysics of personal identity is implicated. When I imagine being someone else, I can be described as imagining that I am the other person-which sounds as if I am imagining a relation of identity between that person and me, David Velleman. As Williams points out, however, this particular way of imagining that I am another person is not really about me or my identity with anyone.2
Identifying local mechanisms for tumor-derived immunosuppression: an integrated phenotypic screening approach

Meeting abstracts Simply stated, clinical response to an immunotherapy is proportional to the product of three quantities: the total number of tumor-infiltrating lymphocytes (TILs), the proportion of tumor cells that can be recognized by these TILs, and the cytotoxic efficacy of TILs directed
Performance determination: the selection of tools, if any

As interest in computer performance analysis has grown, the dedication of some analysts to a single tool and analysis approach appears to have become stronger. In most instances this affection probably comes from increased familiarity and success with an approach combined with a resulting lack of familiarity and success with other approaches.
Magnetic cobalt nanowire thin films.

Two-dimensional (2D) and three-dimensional (3D) magnetic cobalt nanowire thin films with tunable 3−10 nm wire diameters have been electrodeposited using mesoporous silica templates containing 2D hexagonal or 3D cubic pore channels. As compared to bulk cobalt films, the cobalt nanowire thin films exhibit enhanced coercivities and controllable magnetic anisotropy through tuning of the mesostructure and dimension of the nanowires. Such novel magnetic nanowire thin films may provide a new platform for high-density information storage applications.
Multidimensional thermal structure of magnetized neutron star envelopes

Recently launched x-ray telescopes have discovered several candidate isolated neutron stars. The thermal radiation from these objects may potentially constrain our understanding of nuclear physics in a realm inaccessible to terrestrial experiments. To translate the observed fluxes from neutron stars into constraints, one needs precise calculations of the heat transfer through the thin insulating envelopes of neutron stars. We describe models of the thermal structure of the envelopes of neutron stars with magnetic fields up to 10 14 G. Unlike earlier work, we infer the properties of envelope models in two dimensions and precisely account for the quantization of the electron phase space. Both dipole and uniformly magnetized envelopes are considered. Isolated neutron stars can be used as powerful tools for understanding the properties of nuclear matter. The internal structure of neutron stars spans the high-density, low-temperature regime of the QCD phase diagram which is neither constrained by terrestrial experiments such as heavy-ion collisions nor by the properties of the early universe. Both the sizes of neutron stars and their cooling evolution depend crucially on the nuclear equation of state and the species present in the stellar core. The emission that we observe from the surfaces of isolated neutron stars does give a picture of the properties of the nuclear material in the core, but it is a view through the crust of the star. Depending on the properties of the crust, the thermal flux can vary significantly for a fixed core temperature. Fortunately, after the first few hundred years of a neutron star’s life, the core becomes nearly isothermal and cooling proceeds quasistatically. During this era, the neutron star separates thermally into three regions. At the highest densities is the core which provides the thermal inertia. From densities � ∼ 10 10 g/cm 3 down to � ∼ 10 2 g/cm 3 is the envelope which insulates the core thermally from the exterior and which throttles the photon flux from the surface. The lowest density region is the atmosphere which effectively determines the spectrum of the neutron star but not the total flux emitted. In this paper, we focus on the properties of the envelope which will determine the gross properties of the emitted thermal radiation. Although analytic studies (e.g. Heyl & Hernquist 1998; hereafter Paper I) of neutron star envelopes can well characterize the emission from cooling neutron stars, particularly those with either sufficiently weak or strong fields, most potentially observable neutron stars possess field strengths in neither of these limits and have high core temperatures which invalidate the low-temperature approximation used in Paper I. The analytic technique outlined in Paper I assumes that only the first Landau level is filled, that the transition from the highly non-degenerate regime to the highly degenerate regime is abrupt, and
A formula for the core of an ideal

The core of an ideal is the intersection of all its reductions. For large classes of ideals I we explicitly describe the core as a colon ideal of a power of a single reduction and a power of I.
Applications of planar-chiral heterocycles in enantioselective catalysis: Cu(I)/bisazaferrocene-catalyzed asymmetric ring expansion of oxetanes to tetrahydrofurans

Abstract A planar-chiral, C2-symmetric bisazaferrocene ligand is shown to control the stereochemistry of Cu(I)-catalyzed ring expansions of oxetanes to tetrahydrofurans.
Heat pipe thermal control of slender optics probes

The thermal design for a stereographic viewing system is presented. The design incorporates an annular heat pipe and thermal isolation techniques. Test results are compared with design predictions for a prototype configuration. Test data obtained during heat pipe startup showing temperature gradients along the evaporator wall are presented. Correlations relating maximum wall temperature differences to a liquid Reynolds number were obtained at low power levels. These results are compared with Nusselt's Falling Film theory.
WELL-POSED INITIAL-BOUNDARY VALUE PROBLEM FOR A CONSTRAINED EVOLUTION SYSTEM AND RADIATION-CONTROLLING CONSTRAINT-PRESERVING BOUNDARY CONDITIONS

A well-posed initial-boundary value problem is formulated for the model problem of the vector wave equation subject to the divergence-free constraint. Existence, uniqueness and stability of the solution is proved by reduction to a system evolving the constraint quantity statically, i.e. the second time derivative of the constraint quantity is zero. A new set of radiation-controlling constraint-preserving boundary conditions is constructed for the free evolution problem. Comparison between the new conditions and the standard constraint-preserving boundary conditions is made using the Fourier–Laplace analysis and the power series decomposition in time. The new boundary conditions satisfy the Kreiss condition and are free from the ill-posed modes growing polynomially in time.
Ribosomes Pause during the Expression of the Large ATP Synthase Gene Cluster in Spinach Chloroplasts

The large ATP synthase gene cluster from spinach (Spinacia oleracea) chloroplasts encodes five genes, the last four of which encode subunits of the ATP synthase complex. In preliminary experiments (J.K. Kim, M.J. Hollingsworth [1992] Anal Biochem 206: 183–188) it was shown that ribosomes pause during translation of these open reading frames. We have examined ribosome pausing in the four ATP synthase open reading frames of this gene cluster to determine whether it could affect the final ratio of the ATP synthase polypeptides derived from the cluster. Ribosome pauses were mapped and found to be distributed in a nonuniform manner. We have quantitated the relative extent of ribosome pausing within each open reading frame. There is a general but not absolute correlation between the extent of ribosomal pausing and the protein levels found within the ATP synthase complex. We conclude that although it is not the sole factor, ribosome pausing may be a significant posttranscriptional mechanism affecting the expression of the large ATP synthase gene cluster in spinach chloroplasts.
The Recent Star Formation History of the M31 Disk

The star formation history of the northern and southern M31 disk is measured using samples of BV photometry for 4' × 4' regions taken from the KPNO/CTIO Local Group Survey. The distances, mean reddening values, and age distributions of the stars in these regions were measured using the routines of Dolphin. Independent measurements of overlapping fields show that the results are stable for most samples. A slight distance gradient is seen across the major axis of the southern disk, and a mean distance of 24.47 ± 0.03 is found by combining the results. Higher mean reddening values are seen to follow the spiral structure. The stellar age distributions are consistent with episodic star formation confined mainly to the gas-rich arm regions. If these episodes were caused by propagating density waves, the waves did not cause significant star formation episodes in the gas-poor interarm regions. A combination of all of the results provides the total star formation rate for 1.4 deg2 of the M31 disk for six epochs. These results suggest that star formation in the disk declined by ~50% from ~250 to ~50 Myr ago. The lowest star formation rate occurred ~25 Myr ago, followed by a ~20% increase to the present. The mean star formation rate for this large portion of M31 over the past 60 Myr is 0.63 ± 0.07 M⊙ yr-1, suggesting a total mean rate for the disk of ~1 M⊙ yr-1.
Relating graph and term rewriting via Böhm models

Dealing properly with sharing is important for expressing some of the common compiler optimizations as source-to-source transformations, such as common subexpressions elimination, lifting of free expressions and removal of invariants from a loop. Term graph rewriting is a computational model to accommodate these concerns. In this paper we are interested in defining a term model for term graph rewriting systems, which allows us to prove total correctness of those optimizations. We introduce the notion of Bohm tree, and show that for orthogonal term graph rewriting systems, Bohm tree equivalence defines a congruence. Total correctness then follows in a straightforward way from showing that if a programM contains less sharing than a programN, then bothM andN have the same Bohm tree. Using Bohm trees we also show that orthogonal term graph rewriting systems are a correct implementation of orthogonal term rewriting systems. This boils down to showing that the behavior of a term graph can be deduced from its finite approximations, that is, graph rewriting is a continuous operation. Our approach differs from that of other researchers which is based on infinite rewriting.
Computational Modeling of Distinct Neocortical Oscillations Driven by Cell-Type Selective Optogenetic Drive: Separable Resonant Circuits Controlled by Low-Threshold Spiking and Fast-Spiking Interneurons

Selective optogenetic drive of fast spiking interneurons (FS) leads to enhanced local field potential (LFP) power across the traditional “gamma” frequency band (20-80Hz; Cardin et al., 2009). In contrast, drive to regular-spiking pyramidal cells (RS) enhances power at lower frequencies, with a peak at 8 Hz. The first result is consistent with previous computational studies emphasizing the role of FS and the time constant of GABAA synaptic inhibition in gamma rhythmicity. However, the same theoretical models do not typically predict low-frequency LFP enhancement with RS drive. To develop hypotheses as to how the same network can support these contrasting behaviors, we constructed a biophysically principled network model of primary somatosensory neocortex containing FS, RS and low-threshold-spiking (LTS) interneurons. Cells were modeled with detailed cell anatomy and physiology, multiple dendritic compartments, and included active somatic and dendritic ionic currents. Consistent with prior studies, the model demonstrated gamma resonance during FS drive, dependent on the time-constant of GABAA inhibition induced by synchronous FS activity. Lower frequency enhancement during RS drive was replicated only on inclusion of an inhibitory LTS population, whose activation was critically dependent on RS synchrony and evoked longer-lasting inhibition. Our results predict that differential recruitment of FS and LTS inhibitory populations is essential to the observed cortical dynamics and may provide a means for amplifying the natural expression of distinct oscillations in normal cortical processing.
Distributed Fair Resource Allocation in Cellular Networks in the Presence of Heterogeneous Delays

We consider the problem of allocating resources at a base station to many competing flows, where each flow is intended for a different receiver. The channel conditions may be time-varying and different for different receivers. It has been shown in a previous paper that in a delay-free network, a combination of queue-length-based scheduling at the base station and congestion control at the end users can guarantee queue-length stability and fair resource allocation. In this note, we extend this result to wireless networks where the congestion information from the base station is received with a feedback delay at the transmitters
Correspondence and Analyticity

The analyticity properties of the S-matrix in the physical region are determined by the correspondence principle, which asserts that the predictions of classical physics are generated by taking the classical limit of the predictions of quantum theory. The analyticity properties deducible in this way from classical properties include the locations of the singularity surfaces, the rules for analytic continuation around these singularity surfaces, and the analytic character (e.g., pole, logarithmic, etc.) of these singularities. These important properties of the S-matrix are thus derived without using stringent locality assumptions, or the Schroedinger equation for temporal evolution, except for freely moving particles. Sum-over-all-paths methods that emphasize paths of stationary action tend to produce the quantum analogs of the contributions from classical paths. These quantum analogs are derived directly from the associated classical properties by reverse engineering the correspondence-principle connection.
Cosmic Evolution of Black Holes and Spheroids. II. Scaling Relations at z = 0.36

We use high-resolution images obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope to determine morphology, nuclear luminosity, and structural parameters of the spheroidal component for a sample of 20 Seyfert galaxies atz = 0.36. We combine these measurements with spectroscopic information from the Keck Telescope to determine the black hole mass-spheroid luminosity relation (MBH-LB), the fundamental plane (FP) of the host galaxies, and the black hole mass-spheroid velocity dispersion relation (MBH-σ). The FP is consistent with that of inactive spheroids at comparable redshifts. Assuming pure luminosity evolution, we find that the host spheroids had smaller luminosity and stellar velocity dispersion than today for a fixed MBH. The offsets correspond to Δ log LB,0 = 0.40 ± 0.11 ± 0.15 (Δlog MBH= 0.51 ± 0.14 ± 0.19) and Δloge σ = 0.13 ± 0.03 ± 0.05 (Δlog MBH = 0.54 ± 0.12 ± 0.21), respectively, for the MBH-L and M BH-σ relations (the double error bars indicate random and ystematic uncertainties, respectively). A detailed analysis of known systematic errors and selection effects shows that they cannot account for the observed offset. We conclude that the data are inconsistent with pure luminosity evolution and the existence of universal and tight scaling relations. In order to obey the three local scaling relations by z = 0, assuming no significant black hole growth, the distant spheroids have to grow their stellar mass by approximately 60% (Δ log Msph = 0.20 ± 0.14) in the next 4 billion years, while preserving their size and holding their stellar mass-to-light ratio approximately constant. The measured evolution can be expressed as MBH/Msph ∝ (1 + z) 1.5±1.0, consistent with black holes of a few × 10 8 M⊙ completing their growth before their host galaxies. Based on the disturbed morphologies of a fraction of the sample (6/20), we suggest collisional mergers with disk-dominated systems as the physical mechanism driving the evolution. © 2007. The American Astronomical Society. All rights reserved.
A dichotomy for Fatou components of polynomial skew products

We consider polynomial maps of the form f(z,w) = (p(z),q(z,w)) that extend as holomorphic maps of CP^2. Mattias Jonsson introduces in (Math. Ann., 1999) a notion of connectedness for such polynomial skew products that is analogous to connectivity for the Julia set of a polynomial map in one-variable. We prove the following dichotomy: if f is an Axiom-A polynomial skew product, and f is connected, then every Fatou component of f is homeomorphic to an open ball; otherwise, some Fatou component of f has infinitely generated first homology.
Relativistic Few-Body Physics

I discuss different formulations of the relativistic few-body problem with an emphasis on how they are related. I first discuss the implications of some of the differences with non-relativistic quantum mechanics. Then I point out that the principle of special relativity in quantum mechanics implies that the quantum theory has a Poincare symmetry, which is realized by a unitary representation of the Poincare group. This representation can always be decomposed into direct integrals of irreducible representations and the different formulations differ only in how these irreducible representations are realized. I discuss how these representations appear in different formulations of relativistic quantum mechanics and discuss some applications in each of these frameworks.
Measuring managerial equity ownership: a comparison of sources of ownership data

Abstract This paper demonstrates that differences in managerial ownership data cannot explain contradictory empirical evidence on the relation between equity ownership and the entrenchment of managers. Three commonly used sources of managerial equity ownership data are described and contrasted. The Value Line Investment Survey is shown to be a relatively low-cost substitute for the data on beneficial ownership by officers and directors found in corporate proxy statements.
The effect of bid withdrawal in a multi-object auction

The Federal Communications Commission currently utilizes a simultaneous multi-round ascending bid auction to allocate Personal Communication Services licenses. In the auction, participants are allowed to withdraw standing bids at a penalty. The penalty is equal to the maximum of zero or the difference between the value of the withdrawn bid on a license and the highest bid after the withdrawal on that license. The withdrawal rule is designed to assist bidders wishing to assemble combinations of licenses who find themselves stranded with an assortment of licenses for which their bids sum to more than their value. This paper reports results of experiments that examine the effect of the withdrawal rule in environments in which losses can occur if packages of licenses must be assembled piecemeal. The experiments demonstrate that there is a tradeoff with using the rule: efficiency and revenue increase, but individual losses are larger. Furthermore, the increased efficiency does not outweigh the higher prices paid so that bidder surplus falls in the presence of the withdrawal rule.
Interlayer interactions in enantiomeric anticlinic liquid crystalline mixtures

The interlayer interaction coefficient U in the anticlinic phase of enantiomeric binary mixtures was determined by measuring the threshold electric field for the onset of solitary waves. U was found to increase with decreasing temperature in the anticlinic phase for a given enantiomer excess X. The ratio $U(X,\ensuremath{\theta})/U(X=1,\ensuremath{\theta}),$ where $\ensuremath{\theta}$ is the polar angle, was found to be significantly smaller for mixtures with low enantiomer excess than for the optically pure material. The observed behavior is analyzed using a mean-field model for dipole-dipole interactions in adjacent layers.
Effect of finite current channel width on the collisional ion cyclotron instability

Abstract The effect of a finite transverse width, magnetic field-aligned current on the collisional ion cyclotron instability is studied. It is found that a finite current width has a stabilizing influence on the instability and for sufficiently narrow current channels can stabilize the instability. The results are discussed in the context of auroral ionosphere. For example, for typical F region parameters it is found that for wavelengths k y ϱ s ∼ 0.5, the stabilizing effect of the channel width starts to become important for L w ≲ 25 ϱ s ( L w is the current channel width, ϱ s is the ion Larmor radius based on the electron temperature, and k is the transverse wavenumber).
Effect of Atomic Ordering on the Catalytic Activity of Carbon Supported PtM (M = Fe , Co, Ni, and Cu) Alloys for Oxygen Reduction in PEMFCs

Carbon-supported PtM (M = Fe, Co, Ni and Cu) catalysts have been synthesized by precipitating the M n + ions as hydroxides in presence of a commercial carbon-supported Pt catalyst followed by heat treatment in a 90% Ar-10% H 2 mixture at 900°C for 1 h. X-ray diffraction indicates the PtFe and PtCo alloys thus obtained to have an ordered structure while the PtNi and PtCu alloys have a disordered FCC structure. Structural analysis of PtFe and PtCo after annealing at various temperatures 500°C ≤ T ≤ 900°C for 1 h indicates the ordering to be maximized for an annealing temperature of around 600°C. Evaluation of the PtM alloy catalysts for oxygen reduction in proton exchange membrane fuel cells (PEMFCs) indicates that the alloys with the ordered structures have higher catalytic activity with lower polarization losses than Pt and the disordered PtM alloys. With the ordered phases, the activity increases with the extent of ordering. The enhanced catalytic activity is explained based on an optimal structural and electronic features consisting of optimum number of Pt and M nearest neighbors, d-electron density in Pt, atomic configuration on the surface, and Pt-Pt distance.
A MAC Layer Protocol for Priority-based Reliable Multicast in Wireless Ad Hoc Networks

RTS-CTS handshake based protocols achieve "reliable unicast" by eliminating the hidden node problem effectively, however, these solutions are not directly or efficiently gener- alizablefor solving the "reliable multicast"problem; multicast remains as a best-effort operation in wireless ad hoc networks. Here, we present a simple, light-weight, and self- stabilizing MAC protocol, namely busy elimination multiple access (BEMA) protocol, for solving the reliable multicast problem. BE MA grants on-demand access to the channel-rather than assigning fixed slots as in TDMA based approaches-and supports prioritization of traffic, thereby providing a useful building block for applications with reliability and quality-of service requirements.
Bis(tri-n-butylstannyl)benzopinacolate: Preparation and use as a mediator of intermolecular free radical reactions

Bis(tri-n-butylstannyl)benzopinacolate (2) serves as a thermal source of tri-n-butylstannyl radicals and mediates intermolecular coupling of selected alkyl halides to O-benzylformaldoxime and electron deficient olefins. A free radical non-chain mechanism is proposed for these reactions.
A Continuum Model for Void Nucleation by Inclusion Debonding

A cohesive zone model, taking full account of finite geometry changes, is used to provide a unified framework for describing the process of void nucleation from in­itial debonding through complete decohesion. A boundary value problem simulating a periodic array of rigid spherical inclusions in an isotropically hardening elastic-viscoplastic matrix is analyzed. Dimensional considerations introduce a characteristic length into the formulation and, depending on the ratio of this characteristic length to the inclusion radius, decohesion occurs either in a "ductile" or "brittle" manner. The effect of the triaxiality of the imposed stress state on nucleation is studied and the numerical results are related to the description of void nucleation within a phenomenological constitutive framework for progressively cavitating solids. 1 Introduction The nucleation of voids from inclusions and second phase particles plays a key role in limiting the ductility and toughness of plastically deforming solids, including structural metals and composites. The voids initiate either by inclusion cracking or by decohesion of the interface, but here attention is confined to consideration of void nucleation by interfacial decohesion. Theoretical descriptions of void nucleation from second phase particles have been developed based on both continuum and dislocation concepts, e.g., Brown and Stobbs (1971), Argon et al. (1975), Chang and Asaro (1978), Goods and Brown (1979), and Fisher and Gurland (1981). These models have focussed on critical conditions for separation and have not explicitly treated propagation of the debonded zone along the interface. Interface debonding problems have been treated within the context of continuum linear elasticity theory; for example, the problem of separation of a circular cylindrical in­clusion from a matrix has been solved for an interface that supports neither shearing nor tensile normal tractions (Keer et al., 1973). The growth of a void at a rigid inclusion has been analyzed by Taya and Patterson (1982), for a nonlinear viscous solid subject to overall uniaxial straining and with the strength of the interface neglected. The model introduced in this investigation is aimed at describing the evolution from initial debonding through com­plete separation and subsequent void growth within a unified framework. The formulation is a purely continuum one using a cohesive zone (Barenblatt, 1962; Dugdale, 1960) type model for the interface but with full account taken of finite geometry
INVARIANTS OF 3-MANIFOLDS DERIVED FROM FINITE DIMENSIONAL HOPF ALGEBRAS

This paper studies invariants of 3-manifolds derived from certain finite dimensional Hopf algebras via regular isotopy invariants of unoriented links in the blackboard framing. The invariants are based on right integrals for these Hopf algebras. It is shown that the resulting class of invariants is definitely distinct from the class of Witten-Reshetikhin-Turaev invariants. The invariant associated with the quantum double of a finite group G is treated in this context, and is shown to count the number of homomorphisms of the fundamental group of the 3-manifold to the given finite group G.
Atom Economy—A Challenge for Organic Synthesis: Homogeneous Catalysis Leads the Way

Enhancing the efficiency of the synthesis of complex organic products constitutes one of the most exciting challenges to the synthetic chemist. Increasing the catalogue of reactions that are simple additions or that minimize waste production is the necessary first step. Transition metal complexes, which can be tunable both electronically and sterically by varying the metal and/or ligands, are a focal point for such invention. Except for catalytic hydrogenation, such methods have been rare in complex synthesis and virtually unknown for CC bond formation until the advent of cross-coupling reactions. These complexes may orchestrate a variety of CC bond-forming processes, important for creation of the basic skeleton of the organic structure. Their ability to insert into CH bonds primes a number of different types of additions to relatively nonpolar π-electron systems. Besides imparting selectivity, they make feasible reactions that uncatalyzed were previously unknown. The ability of these complexes to preorganize π-electron systems serves as the basis both of simple additions usually accompanied by subsequent hydrogen shifts and of cycloadditions. The ability to generate “reactive” intermediates under mild conditions also provides prospects for new types of CC bond-forming reactions. While the examples reveal a diverse array of successes, the opportunities for new invention are vast and largely untapped.
Simulations of mixed-morphology supernova remnants with anisotropic thermal conduction

We explore the role of anisotropic thermal conduction on the evolution of supernova remnants (SNRs) through interstellar media with a range of densities via numerical simulations. We find that a remnant expanding in a dense environment can produce centre-bright hard X-ray emission within 20 kyr, and centre-bright soft X-ray emission within 60 kyr of the supernova event. In a more tenuous environment, the appearance of a centre-bright structure in hard X-rays is delayed until about 60 kyr. The soft X-ray emission from such a remnant may not become centre bright during its observable lifetime. This can explain the observations that show that mixed-morphology SNRs preferentially occur close to denser, molecular environments. Remnants expanding into denser environments tend to be smaller, making it easier for thermal conduction to make large changes in the temperatures of their hot gas bubbles. We show that the lower temperatures make it very favourable to use high-stage ions as diagnostics of the hot gas bubbles in SNRs. In particular, the distribution of O VIII transitions from shell bright at early epochs to centre bright at later epochs in the evolution of an SNR expanding in a dense interstellar medium when the physics of thermal conduction is included.
The Long-Run Impacts of Adult Deaths on Older Household Members in Tanzania

HIV/AIDS is drastically changing the demographic landscape in high-prevalence countries in Africa. The prime-age adult population bears the majority of the mortality burden. These missing prime-age adults have implications for the socioeconomic well-being of surviving family members. This study uses a 13-year panel from Tanzania to examine the impacts of prime-age mortality on the time use and health outcomes of older adults, with a focus on long-run impacts and gender dimensions. Prime-age deaths are weakly associated with increases in working hours of older women when the deceased adult was co-resident in the household. The association is strongest when the deceased adult was living with the elderly individual at the time of death and for deaths in the distant past, suggesting that shorter-run studies may not capture the full extent of the consequences of adult mortality for survivors. Holding more assets seems to buffer older adults from having to work more after these shocks. Most health indicators are not worse for older adults when a prime-age household member died, although more distant adult deaths are associated with an increased probability of acute illness for the surviving elderly. For deaths of children who were not residing with their parents at baseline, the findings show no impact on hours worked or health outcomes.
New Generation Low Power Radiation Survey Instruments

A number of new, ultra-low-powered radiation instruments have recently been developed at Los Alamos. Among these are two instruments which use a novel power source to eliminate costly batteries. The newly developed gamma detecting radiac, nicknamed the Firefly, and the alpha particle detecting instrument, called the Simple Cordless Alpha Monitor, both use recent advances in miniaturization and power-saving electronics to yield devices which are small, rugged, and very power-frugal. The two instruments consume so little power that the need for batteries to run them is eliminated. They are, instead, powered by a charged capacitor which will operate the instruments for an hour or more. Use of a capacitor as a power source eliminates many problems commonly associated with battery-operated instruments, such as having to open the case to change batteries, battery storage life, availability of batteries in the field, and some savings in weight. Both line power and mechanical sources are used to charge the storage capacitors which power the instruments.
Shellside Waterflow-Induced Tube Vibration in Heat Exchanger Configurations With Tube Pitch-to-Diameter Ratio of 1.42

The pitch-to-diameter ration (P/D) of the tube layout in shell-and-tube heat exchangers is one of the major parameters available to the designer to control heat transfer and pressure drop as well as to facilitate mechanical cleaning. As part of a comprehensive investigation of waterflow-induced tube vibration in an industrial-size research heat exchanger, various configurations characterized by different design parameters including P/D ratio had been investigated. To provide a comparison with previous data obtained with P/D = 1.25, this paper presents the results of a study of eight different tube bundle configurations with P/D = 1.42. Four equilaterally spaced tube layout patterns and two baffle edge orientations were investigated. The results indicate that the greater flow area of the P/D = 1.42 configuration increases flow penetration into the bundle, reduces the tube-to-tube vibration coupling, and generally provides less well defined, even though sometimes improved, fluidelastic instability thresholds. 8 refs., 8 figs., 1 tab.
Schubert polynomials for the affine Grassmannian

Let G be a complex simply connected simple group and K a maximal compact subgroup. Let F = C((t)) denote the field of formal Laurent series and O = C[[t]] the ring of formal power series. The quotient Qr = G(F)/G(0) is known as the affine Grassmannian of G. It is known that Qr is homotopy equivalent to the space of based loops ?K into the compact group K (see [9, 30]). The multiplication on QK endows the homology H* (Qr) and cohomology H* (Qr) with structures of dual Hopf algebras. These Hopf algebras were first identified by Bott [4] (another descrip tion is given by Ginzburg [10], which we shall not use). The Bruhat decomposition of G(F) induces a stratification of Qr by Schubert cells ilw, indexed by Grassman nian elements w of the affine Weyl group WaffWe denote by aw G H*(Qr) and aw G H* (Qr) the Schubert classes in homology and cohomology. When G = SL(n,C), Bott identifies H*(Qr) and H*(Qr) with a subring An and a quotient An of the ring of symmetric functions. Our main theorem (Theorem 7.1) identifies the Schubert classes aw G ?* (Qr) and aw G H* (Qr) as explicit symmet ric functions under this isomorphism. These symmetric functions are combinatori ally defined: in homology the aw G H*(Qr) are represented by Lascoux-Lapointe Morse's fc-Schur functions Sw(x) G An and in cohomology the aw G H*(Qr) are represented by the dual fc-Schur functions (or affine Schur functions) Fw(x) G An; see [21, 24, 17]. Our theorem was originally conjectured by Mark Shimozono (the conjecture was made explicit in the cohomology case by Jennifer Morse). Kostant and Kumar [14] studied the topology of homogeneous spaces for arbi trary Kac-Moody groups and in particular calculated the structure constants of H* (Qr) in the Schubert basis, using the algebraic construction of the nilHecke ring. Our connection between the topology and the combinatorics proceeds via the study of three subalgebras of the nilHecke ring. The first subalgebra is the nilCoxeter al gebra Ao, which is the algebra generated by the "divided difference" operators. The second algebra is a certain centralizer algebra ^Aaff (S) which we call the Peterson subalgebra. Peterson [28] constructs an isomorphism j from the T-equivariant ho mology Hr(Qr) of the affine Grassmannian to Z&&ff(S). The third algebra B is a combinatorially defined subalgebra of A0, which we call the (affine) Fomin-Stanley
A limit theorem for a smooth class of semiparametric estimators

Abstract We consider an econometric model based on a set of moment conditions which are indexed by both a finite-dimensional vector of interest, θ, and an infinite-dimensional parameter, h, which in turn depends upon both θ and another infinite-dimensional parameter, τ. The population moment conditions equal zero at θ = θ0. Estimators of θ0 are obtained by forming nonparametric estimates of h and τ, substituting them into the sample analog of the moment conditions, and choosing that value of θ that makes the sample moments as ‘close as possible’ to zero. Using independence and smoothness assumptions the paper provides consistency, √n consistency, and asymptotic normality proofs for the resultant estimator. As an example, we consider Olley and Pakes' (1991) use of semiparametric techniques to control for both simultaneity and selection biases in estimating production functions. The example illustrates how semiparametric techniques an be used to overcome both computational problems and the need for strong functional form restrictions in obtaining estimates from structural models. It also illustrates the impacts of 1. (i) alternative estimators for the nonparametric components of the problem and 2. (ii) alternative estimators for the standard errors of the estimated θ.
Improving Gated Cardiac Scanning Using Limited-Angle Reconstruction Technique

Selected phases of the cardiac cycle can be imaged by the method of gated cardiac scanning using whole body scanners. However, since there is no synchronization between the random heart beats and the CT machine, the output will have gaps in the angular coverage of each scan. The missing projections in these gaps result in artifacts in the reconstructed images. In this paper the technique of limited-angle reconstruction is employed to fill in the missing projections to remove the artifacts. The object is transformed back and forth between the object space and the projection space, being corrected in each step by the constraints of the finite spatial extent and of the upper and lower bounds of the object in the object space, and the known projections in the projection space. It is found that by using the proposed algorithm the rms errors of the limited-angle images are reduced to a level comparable to those of the complete-angle images. The same iteration algorithm can also be used to reduce the fan beam scanning angle from 360 degree to 180 degree without sacrificing much image quality.
On relations between vertex operators, quasiclassical operators, and phase space coordinates

Abstract For certain situations we give a geometrical background for quasiclassical Kadomtsev-Petviashvili (KP) equation calculations based on an explicit connection to quantum mechanics and the collapse of coherent states to coadjoint orbits for classical operators.
Reactions of osmium tetroxide with imidazoles

Abstract We have studied the reactions of imidazoles with osmium tetroxide both in the presence and absence of ligands other than imidazoles. The pathway involves: (1) osmium tetroxide-ligand complexation (fast), (2) addition of osmium tetroxide to the 4,5-double bond of the imidazole to form the cyclic osmium(VI) ester (slow), and (3) degradation of the osmate ester via ring cleavage of the 4,5-dihydroxydihydroimidazole (very slow). We report kinetic data for addition to the double bond as a function of imidazole structure. The final product is an osmate(VI) ester of a 4,5-dihydroxydihydroimidazole with two imidazole molecules (or other ligands) occupying the remaining coordination sites. We present evidence, both kinetic and chemical, for an intermediate containing only one such ligand.
Discovery of the cerium isotopes

The discovery of the 35 cerium isotopes presently known is discussed. Criteria for the discovery of isotopes are suggested and for each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.
(Why) Do self-employed parents have more children?

Using data from the U.S. Census, we find that married self-employed men have between 0.1 and 0.2 more children as compared to if they are not self-employed. This is consistent with the hypothesis that self-employed households have a preference for larger families to raise the likelihood that an inside family member will be a good match at running the business. This empirical relationship is established using a regression framework, including the use of instrumental variables estimation to allow for the possibility of endogeneity of the respondent’s self-employment status and whether the respondent’s spouse stays at home. Moreover, we find a slightly higher demand for sons among the self employed who are over 40 at the time of the 1990 U.S. Census: namely, given the exogenous variation in gender mix of prior children, self employed parents born prior to 1950 appear to have an increased demand for a third child if the first two children were not sons. This effect does disappear, however, for the later generation of respondents.