cssi/SciSciGPT-SciSciNet huggingface dataset:
Complete collineations revisited

The space of complete collineations is a compactification of the space of matrices of fixed dimension and rank, whose boundary is a divisor with normal crossings. It was introduced in the 19th century and has been used to solve many enumerative problems. We show that this venerable space can be understood using the latest quotient constructions in algebraic geometry. Indeed, there is a detailed analogy between the complete collineations and the moduli space of stable pointed curves of genus zero. The remarkable results of Kapranov exhibiting the latter space as a Chow quotient, Hilbert quotient, and so on, all have counterparts for complete collineations. This analogy encompasses Vainsencher's construction of the complete collineations, as well as a form of the Gel'fand-MacPherson correspondence. There is also a tangential relation with the Gromov-Witten invariants of Grassmannians. The symmetric and anti-symmetric versions of the problem are considered as well. An appendix explains the original motivation, which came from the space of broken Morse flows for the moment map of a circle action.
Salt-Induced Collapse and Reexpansion of Highly Charged Flexible Polyelectrolytes

We study the salt-dependent conformations of dilute flexible polyelectrolytes in solution via computer simulations. Low concentrations of multivalent salt induce the known conformational collapse of individual polyelectrolyte chains, but as the salt concentration is increased further this is followed by a reexpansion. We explicitly demonstrate that multivalent counterions can overcompensate the bare charge of the chain in the reexpansion regime. Both the degree of reexpansion and the occurrence of overcharging sensitively depend on ion size. Our findings are relevant for a wide range of salt-induced complexation phenomena.
Low energy antideuterons: shedding light on dark matter

Low energy antideuterons suffer a very low secondary and tertiary astrophysical background, while they can be abundantly synthesized in dark matter pair annihilations, therefore providing a privileged indirect dark matter detection technique. The recent publication of the first upper limit on the low energy antideuteron flux by the BESS Collaboration, a new evaluation of the standard astrophysical background, and remarkable progress in the development of a dedicated experiment, GAPS, motivate a new and accurate analysis of the antideuteron flux expected in particle dark matter models. To this extent, we consider here supersymmetric, universal extra-dimensional (UED) Kaluza–Klein and warped extra-dimensional dark matter models, and assess both the prospects for antideuteron detection and the various related sources of uncertainties. The GAPS experiment, even in a preliminary balloon-borne set-up, will explore many supersymmetric configurations, and, eventually, in its final space-borne configuration, will be sensitive to primary antideuterons over the whole cosmologically allowed UED parameter space, providing a search technique which is highly complementary with other direct and indirect dark matter detection experiments.
Acceleration-induced nonlocality: kinetic memory versus dynamic memory

The characteristics of the memory of accelerated motion in Minkowski spacetime are discussed within the framework of the nonlocal theory of accelerated observers. Two types of memory are distinguished: kinetic and dynamic. We show that only kinetic memory is acceptable, since dynamic memory leads to divergences for nonuniform accelerated motion.
Modular stratification and magic sets for Datalog programs with negation

A class of “modularly stratified” logic programs is defined. Modular stratification generalizes stratification and local stratification, while allowing programs that are not expressible as stratified programs. For modularly stratified programs, the well-founded semantics coincides with the stable model semantics and makes every ground literal true or false. Modularly stratified programs are weakly stratified, but the converse is false. Unlike some weakly stratified programs, modularly stratified programs can be evaluated in a subgoal-at-a time fashion. An extension of top-down methods with memoing that handles this broader class of programs is presented. A technique for rewriting a modularly stratified program for bottom-up evaluation is demonstrated and extended to include magic-set techniques. The rewritten program, when evaluated bottom-up, gives correct answers according to the well-founded semantics, but much more efficiently than computing the complete well-founded model. A one-to-one correspondence between steps of the extended top-down method and steps during the bottom-up evaluation of the magic-rewritten program is exhibited, demonstrating that the complexity of the two methods is the same. Extensions of modular stratification to other operators such as set-grouping and aggregation, which have traditionally been stratified to prevent semantic difficulties, are discussed.
Ballistic Impact of Thin-Walled Composite Structures

Methods of analysis have been developed that provide the means to determine whether a ballistic impactor of known shape, mass, and striking velocity will penetrate a given thin-walled composite material structure and if it does, what the residual velocity of the impactor will be. The methods developed require performing penetration experiments at two striking velocities (with suitable replicates for statistical purposes) for any given composite structural target. From this minimum number of tests, one can predict the penetration, nonpenetration, and residual velocity of an impact at other striking velocities. This provides a dramatic reduction in the amount of expensive testing required to study penetration due to ballistic impact. It also provides a less expensive and less time-consuming means to select the best material system and structural configuration to resist ballistic impact. Finally, it shows that the physics of ballistic impact and the penetration phenomena is modeled satisfactorily. These methods also accurately predict the ballistic limit.
Analytical framework for gain scheduling

The gain scheduling approach to the control of nonlinear systems is explained, and its characteristics are examined. On the basis of this framework questions are raised, and implications are drawn for practical design situations. The relationship between the gain scheduling formulation and the extended-linearization approach for nonlinear control design is considered. >
Chondrule-forming shock fronts in the solar nebula: A possible unified scenario for planet and chondrite formation

Chondrules are millimeter-sized spherules found throughout primitive chondritic meteorites. Flash heating by a shock front is the leading explanation of their formation. However, identifying a mechanism for creating shock fronts inside the solar nebula has been difficult. In a gaseous disk capable of forming Jupiter, the disk must have been marginally gravitationally unstable at and beyond Jupiter's orbit. We show that this instability can drive inward spiral shock fronts with shock speeds of up to ~10 km s-1 at asteroidal orbits, sufficient to account for chondrule formation. The mixing and transport of solids in such a disk, combined with the planet-forming tendencies of gravitational instabilities, results in a unified scenario linking chondrite production with gas giant planet formation.
Total Synthesis of (±)- and (−)-Actinophyllic Acid

Development of efficient sequences for the total syntheses of (±)-actinophyllic acid (rac-1) and (−)-actinophyllic acid (1) are described. The central step in these syntheses is the aza-Cope/Mannich reaction, which constructs the previously unknown hexacyclic ring system of actinophyllic acid in one step from much simpler tetracyclic precursors. The tetracyclic hexahydro-1,5-methano-1H-azocino[4,3-b]indole ketone rac-37 is assembled from o-nitrophenylacetic acid in four steps, with oxidative cyclization of a dienolate derivative of tricyclic precursor rac-35 being the central step. In the first-generation synthesis, this intermediate is transformed in two steps to homoallyl amine rac-43, whose formaldiminium derivative undergoes efficient aza-Cope/Mannich reaction to give pentacyclic ketone rac-44. In four additional steps, this intermediate is advanced to (±)-actinophyllic acid. The synthesis is streamlined by elaborating ketone rac-37 to β-hydroxyester intermediate rac-53, which is directly transformed ...
High School Dropouts and Sexually Transmitted Infections.

People who drop out of high school fare worse in many aspects of life. We analyze the relationship between dropping out of high school and the probability of contracting a sexually transmitted infection (STI). Previous studies on the relationship between dropout status and sexual outcomes have not empirically addressed unobserved heterogeneity at the individual level. Using fixed effects estimators, we find evidence supporting a positive relationship between dropping out of high school and the risk of contracting an STI for females. Furthermore, we present evidence that illustrates differences between the romantic partners of dropouts versus enrolled students. These differences suggest that female dropouts may be more susceptible to contracting STIs because they partner with significantly different types of people than do nondropouts. Our results point to a previously undocumented benefit of encouraging those at risk of dropping out to stay in school longer.
Mechanism of Chemical Glycosylation: Focus on the Mode of Activation and Departure of Anomeric Leaving Groups

Many glycosyl donors used in chemical glycosylation are too stable to undergo spontaneous glycosylation. Hence, the first key step of practically every glycosylation reaction is the activation of the leaving group that usually takes place via its interaction with a promoter/activator or, more rarely, a catalyst. The focus of this review is the first key step of glycosylation with the emphasis on the modes by which the leaving groups are activated and departed. Studies wherein the exact nature of the activation process has been reliably elucidated are still scarce. Therefore, this review particularly details the mechanistic studies wherein the mode of activation was proven either by characterizing the activated intermediates or by isolation of the departed leaving group–activator adducts.
Coalescing binary neutron stars

Coalescing compact binaries with neutron star or black hole components provide the most promising sources of gravitational radiation for detection by the LIGO/VIRGO/GEO/TAMA laser interferometers now under construction. This fact has motivated several different theoretical studies of the inspiral and hydrodynamic merging of compact binaries. Analytic analyses of the inspiral waveforms have been performed in the post-Newtonian approximation. Analytic and numerical treatments of the coalescence waveforms from binary neutron stars have been performed using Newtonian hydrodynamics and the quadrupole radiation approximation. Numerical simulations of coalescing black hole and neutron star binaries are also underway in full general relativity. Recent results from each of these approaches will be described and their virtues and limitations summarized.
Iterative Stereospecific Reagent-Controlled Homologation of Pinacol Boronates by Enantioenriched α-Chloroalkyllithium Reagents

Reaction of pinacol boronates with putative enantioenriched α-chloroalkyllithium species, generated in situ from homochiral α-chloroalkylsulfoxides by sulfoxide ligand exchange with t-BuLi in PhMe at −78 °C, gave chain-extended boronic ester products with generally excellent stereochemical fidelity. Iteration of this stereospecific reagent-controlled homologation (StReCH) process enabled the programmed synthesis of all four stereoisomers of a stereodiad-containing model system (4-benzyl-1,6-diphenylhexan-2-ol) with er ≥ 97:3 in all cases.
Simulation design of a multiprocessing system

Since 1965 the IBM Corporation and the MITRE Corporation have been involved in the design and implementation of the Enroute Stage A Air Traffic Control (ATC) System of the National Airspace System (NAS). The National Airspace System, as conceived by the Federal Aviation Agency (FAA), will provide advanced air traffic control capabilities in the late 1960's and early 1970's through the use of real time computing systems, thereby automating the data management functions of today's controllers. The system will automate 20 Air Route Traffic Control Centers (ARTCC) throughout the United States.
Computing instanton numbers of curve singularities

We present an algorithm for computing instanton numbers of curve singularities. A comparison is made between these and some other invariants of curve singularities. The algorithm is implemented in Macaulay2, and can be downloaded from http://www.math.nmsu.edu/~iswanson/instanton.m2 or from http://emmy.nmsu.edu/~gasparim/m2code.
E-State Modeling of Dopamine Transporter Binding. Validation of the Model for a Small Data Set.

Data for 25 tropane analogues binding to the dopamine transporter were modeled using E-state molecular structure descriptors. Both E-state and hydrogen E-state descriptors appear in the model in both atom-level and atom-type descriptors. A statistically satisfactory four-variable model is obtained, and structure interpretation is given for each variable, emphasizing substituent influence on nonpolar parts of the molecule as well as the role of hydrogen bonding. A leave-group-out approach to model validation is presented in which each observation is removed from the data set three times in random groups of 20% of the whole data set. The average of the resulting predicted values constitutes consensus predictions for these data and supports the claim that the E-state model may be useful for prediction of pIC50 values for new compounds.
On the Closest Vector Problem with a Distance Guarantee

We present a new efficient algorithm for the search version of the approximate Closest Vector Problem with Preprocessing (CVPP). Our algorithm achieves an approximation factor of O(n/sqrt{log n}), improving on the previous best of O(n^{1.5}) due to Lag arias, Lenstra, and Schnorr {hkzbabai}. We also show, somewhat surprisingly, that only O(n) vectors of preprocessing advice are sufficient to solve the problem (with the slightly worse approximation factor of O(n)). We remark that this still leaves a large gap with respect to the decisional version of CVPP, where the best known approximation factor is O(sqrt{n/log n}) due to Aharonov and Regev {AharonovR04}. To achieve these results, we show a reduction to the same problem restricted to target points that are close to the lattice and a more efficient reduction to a harder problem, Bounded Distance Decoding with preprocessing (BDDP). Combining either reduction with the previous best-known algorithm for BDDP by Liu, Lyubashevsky, and Micciancio {LiuLM06} gives our main result. In the setting of CVP without preprocessing, we also give a reduction from (1+eps)gamma approximate CVP to gamma approximate CVP where the target is at distance at most 1+1/eps times the minimum distance (the length of the shortest non-zero vector) which relies on the lattice sparsification techniques of Dadush and Kun {DadushK13}. As our final and most technical contribution, we present a substantially more efficient variant of the LLM algorithm (both in terms of run-time and amount of preprocessing advice), and via an improved analysis, show that it can decode up to a distance proportional to the reciprocal of the smoothing parameter of the dual lattice {MR04}. We show that this is never smaller than the LLM decoding radius, and that it can be up to an wide tilde{Omega}(sqrt{n}) factor larger.
Generation, trapping and fate of alkylidenecarbene-iodonium ylides from the addition of NaN3 to alkynylphenyliodonium tosylates

Abstract Addition of NaN3 to RCC I + Ph· O − Ts results in novel alkylidenecarbene-iodonium ylides, 5, R(N3)CCIPh, that by either protonation, ylide transfer or insertion of the derived carbene R(N3)CC: give unique functionalized vinyl azides.
Axioms for memory access in asynchronous hardware systems

The problem of concurrent accesses to registers by asynchronous components is considered. A set of axioms about the values in a register during concurrent accesses is proposed. It is shown that if these axioms are met by a register, then concurrent accesses to it may be viewed as nonconcurrent, thus making it possible to analyze asynchronous algorithms without elaborate timing analysis of operations. These axioms are shown, in a certain sense, to be the weakest. Motivation for this work came from analyzing low-level hardware components in a VLSI chip which concurrently accesses a flip-flop.
Time‐dependent dynamics of methyl iodide photodissociation in the first continuum

The photodissociation dynamics of methyl iodide (CH3I) and its deuterated counterpart (CD3I) in the A band is studied using a time‐dependent quantum mechanical method, based on the fast Fourier transform (FFT) method of Kosloff and Kosloff. The calculation uses a pseudotriatomic approximation in which the umbrella mode of CH3 (CD3) is approximated by a C–X (X=H3, D3) stretch. In addition, the I–C–X dissociation is assumed collinear and angular momentum is ignored. The wave packet is propagated on coupled electronic potential surfaces which we have developed by revising Shapiro’s potentials to fit recent experimental data. Good agreement between our calculations and experiment has been obtained for the absorption spectrum, the vibrational distributions for the methyl umbrella mode, and I*/I branching ratios for both CH3I and CD3I at 248 nm. According to our model, the CH3 fragment in the I* channel at 266 nm is predominantly at its ground vibrational state, while the vibrational distribution in the lower I...
Infrared Colors and Variability of Evolved Stars from COBE DIRBE Data

For a complete 12 ?m flux-limited sample of 207 IRAS sources (F12 ? 150 Jy, |b| ? 5?), the majority of which are AGB stars (~87%), we have extracted light curves in seven infrared bands between 1.25 and 60 ?m using the database of the Diffuse Infrared Background Experiment (DIRBE) instrument on the Cosmic Background Explorer (COBE) satellite. Using previous infrared surveys, we filtered these light curves to remove data points affected by nearby companions and obtained time-averaged flux densities and infrared colors, as well as estimates of their variability at each wavelength. In the time-averaged DIRBE color-color plots, we find clear segregation of semiregulars, Mira variables, carbon stars, OH/IR stars, and red giants without circumstellar dust (i.e., V-[12] < 5) and with little or no visual variation (?V < 0.1 mag). The DIRBE 1.25?25 ?m colors become progressively redder and the variability in the DIRBE database increases along the oxygen-rich sequence nondusty slightly varying red giants?SRb/Lb?SRa?Mira?OH/IR and the carbon-rich SRb/Lb?Mira sequence. This supports previous assertions that these are evolutionary sequences involving the continued production and ejection of dust. The carbon stars are redder than their oxygen-rich counterparts for the same variability type, except in the F12/F25 ratio, where they are bluer. Of the 28 sources in the sample not previous noted to be variable, 18 are clearly variable in the DIRBE data, with amplitudes of variation of ~0.9 mag at 4.9 ?m and ~0.6 mag at 12 ?m, consistent with them being very dusty Mira-like variables. We also present individual DIRBE light curves of a few selected stars. The DIRBE light curves of the semiregular variable L2 Pup are particularly remarkable. The maxima at 1.25, 2.2, and 3.5 ?m occur 10?20 days before those at 4.9 and 12 ?m, and, at 4.9 and 12 ?m, another maximum is seen between the two near-infrared maxima.
Thomas-Fermi charge mixing for obtaining self-consistency in density functional calculations

We present a method for charge mixing in self-consistent density functional calculations which uses the Thomas-Fermi-von Weizs\"acker equation to solve implicitly for the charge density response function to the potential. This approach has significant improvements over existing methods, particularly for inhomogeneous systems with large unit cells which commonly suffer from poor convergence due to charge sloshing.
On the Detectability of Oxygen X-Ray Fluorescence and Its Use as a Solar Photospheric Abundance Diagnostic

Monte Carlo calculations of the O Kα line fluoresced by coronal X-rays and emitted just above the temperature minimum region of the solar atmosphere have been employed to investigate the use of this feature as an abundance diagnostic. While they are quite weak, we estimate line equivalent widths in the range 0.02-0.2 A, depending on the X-ray plasma temperature. The line remains essentially uncontaminated by blends for coronal temperatures T ≤ 3 × 106 K and should be quite observable, with a flux 2 photons s−1 arcmin−2. Model calculations for solar chemical mixtures with an O abundance adjusted up and down by a factor of 2 indicate 35%-60% changes in O Kα line equivalent width, providing a potentially useful O abundance diagnostic. Sensitivity of equivalent width to differences between recently recommended chemical compositions with "high" and "low" complements of the CNO trio important for interpreting helioseismological observations is less acute, amounting to 20%-26% at coronal temperatures T ≤ 2 × 106 K. While still feasible for discriminating between these two mixtures, uncertainties in measured line equivalent widths and in the models used for interpretation would need to be significantly less than 20%. Provided a sensitive X-ray spectrometer with resolving power ≥1000 and suitably well-behaved instrumental profile can be built, X-ray fluorescence presents a viable means for resolving the solar "oxygen crisis."
The origins and dynamics of production networks in Silicon Valley

Abstract Computer systems firms in Silicon Valley are responding to rising costs of product development, shorter product cycles and rapid technological change by focusing and building partnerships with suppliers, both within and outside of the region. Well-known firms like Hewlett-Packard and Apple Computers and lesser known ones like Silicon Graphics and Pyramid Technology are organized to combine the components and sub-systems made by specialist suppliers into new computer systems. As these firms collaborate to both define and manufacture new systems, they are institutionalizing their capacity to learn from one another. Three cases a contract manufacturer, a silicon foundry, and the joint development of a microprocessor - illustrate how inter-firm networks help account for the sustained technological dynamism of the regional economy.
Congenital absence of the uterus and vagina is not commonly transmitted as a dominant genetic trait: Outcomes of surrogate pregnancies

Objective To determine the inheritance pattern of congenital absence of the uterus and vagina in affected women undergoing surrogacy IVF with this disorder. Design Retrospective study. Setting A hospital-based reproductive endocrinology and infertility center. Patient(s) Women diagnosed with congenital absence of the uterus and vagina undergoing IVF with subsequent transfer of embryos to a surrogate uterus. Intervention(s) Questionnaires were sent to all infertility treatment centers performing surrogate procedures. Main Outcome Measure(s) Number, gender, and frequency of congenital anomalies in progeny. Result(s) Thirty-two of 53 surveyed programs responded (60%). One hundred sixty-two IVF cycles were performed, and 34 liveborn children were delivered (half female). No congenital anomalies were found, except for one male child with a middle ear defect and hearing loss. Conclusion(s) These results strongly suggest that congenital absence of the uterus and vagina, if genetically transmitted, is not inherited commonly in a dominant fashion. Fertil Steril ® 1997;67:387-9
Protecting against key-exposure: strongly key-insulated encryption with optimal threshold

Key-insulated encryption schemes use a combination of key splitting and key evolution to protect against key exposure. Existing schemes, however scale poorly, having cost proportional to the number t of time periods that may be compromised by the adversary, and thus are practical only for small values of t. Yet in practice t might be large.This paper presents a strongly key-insulated encryption scheme with optimal threshold. In our scheme, t need not be known in advance and can be as large as one less than the total number of periods, yet the cost of the scheme is not impacted. This brings key-insulated encryption closer to practice. Our scheme is based on the Boneh-Franklin identity-based encryption (IBE) scheme [9], and exploits algebraic properties of the latter.Another contribution of this paper is to show that (not strongly) key-insulated encryption with optimal threshold and allowing random-access key updates (which our scheme and all others known allow) is equivalent to a restricted form of IBE. This means that the connection between key-insulated encryption and IBE is not accidental.
Equilibration of granular subsystems

We experimentally investigate the steady states of two granular assemblies differing in their material properties and allowed to exchange volume with each other under external agitation in the vicinity of their jamming transition. We extract the statistics of various static and dynamic quantities, and uncover a materials-independent relationship between the average packing fraction and its fluctuations. This relationship defines an intensive parameter which decouples from the volume statistics, and remarkably takes the same value in both subsystems. We also observe that an effective diffusion coefficient also takes the same value in each subsystem, even as the structural relaxation time increases over several orders of magnitude. These observations provide strong constraints on the eventual establishment of a granular equation of state.
25th anniversary article: Understanding the lithiation of silicon and other alloying anodes for lithium-ion batteries

Alloying anodes such as silicon are promising electrode materials for next-generation high energy density lithium-ion batteries because of their ability to reversibly incorporate a high concentration of Li atoms. However, alloying anodes usually exhibit a short cycle life due to the extreme volumetric and structural changes that occur during lithium insertion/extraction; these transformations cause mechanical fracture and exacerbate side reactions. To solve these problems, there has recently been significant attention devoted to creating silicon nanostructures that can accommodate the lithiation-induced strain and thus exhibit high Coulombic efficiency and long cycle life. In parallel, many experiments and simulations have been conducted in an effort to understand the details of volumetric expansion, fracture, mechanical stress evolution, and structural changes in silicon nanostructures. The fundamental materials knowledge gained from these studies has provided guidance for designing optimized Si electrode structures and has also shed light on the factors that control large-volume change solid-state reactions. In this paper, we review various fundamental studies that have been conducted to understand structural and volumetric changes, stress evolution, mechanical properties, and fracture behavior of nanostructured Si anodes for lithium-ion batteries and compare the reaction process of Si to other novel anode materials.
Existence and Uniqueness of Constant Mean Curvature Foliation of Asymptotically Hyperbolic 3-Manifolds

We prove existence and uniqueness of foliations by stable spheres with constant mean curvature for 3-manifolds which are asymptotic to anti-de Sitter–Schwarzschild metrics with positive mass. These metrics arise naturally as spacelike timeslices for solutions of the Einstein equation with a negative cosmological constant.
Effects of Olefin Substitution on the Ring-Closing Metathesis of Dienes

Ruthenium alkylidene 1 and molybdenum alkylidene 2 have been utilized in the ring-closing metathesis (RCM) of dienes containing gem-disubstituted olefins to yield tri- and tetrasubstituted cyclic olefins. Dienes with sterically demanding and/or electron-withdrawing substituents such as Ph, CO(2)Me, and (t)()Bu were cyclized successfully with 2, but did not cyclize with 1. Tetrasubstituted cyclic olefins could be formed with 2, but not using alkylidene 1. Dienes with allylic functional groups yielded functionalized cyclic olefins when treated with 1.
Kinematics of Star Clusters in M33: Distinct Populations

We present velocity measurements for 107 star clusters in the nearby, low-luminosity spiral galaxy M33, from a homogeneous data set taken with the WIYN HYDRA spectrograph. The target clusters were chosen primarily from our previous catalogs based on multiband Hubble Space Telescope WFPC2 imaging and therefore have previous age estimates based on integrated colors. Our sample includes objects spanning the entire range of cluster ages found in M33, allowing us to study cluster kinematics as a function of age. We find that the cluster velocity dispersion with respect to the local disk motion increases dramatically with age. The young clusters have a maximum circular velocity of 87 ± 11 km s-1, similar to the previous rotation solution for H II regions in M33. When clusters are divided into age groups, the old clusters clearly have very different kinematics from the young population and from the gas disk. Monte Carlo simulations comparing synthetic disk plus halo systems with the observed velocity distribution for our old M33 clusters suggest that old clusters are likely to be composed of two distinct subpopulations, an 85% ± 5% halo component plus a 15% ± 5% disk component. This is the first evidence for distinct kinematic subpopulations among the old M33 clusters, and this galaxy appears to have a higher halo/bulge fraction of old stellar objects than found in the Galaxy. To further study the properties of halo clusters in M33, we use spectroscopic line index measurements for 17 clusters with the largest departure from disk motion, and thus the most pristine halo objects in our sample, to determine ages and approximate metal abundances. When compared with the Worthey models and with similar measurements for 12 Galactic globulars, our clusters have an age spread of ~5-7 Gyr, ~2 times as large as the spread among the Galactic sample. This small halo sample shows little evidence for a progression in metal abundance with age. There is also some support for different size (core radius) distributions when comparing "young" and "old" halo M33 clusters. We discuss these findings in the context of different galaxy formation models.
From Chance to Choice: Genetics and Justice

This book, written by four internationally renowned bioethicists and first published in 2000, was the first systematic treatment of the fundamental ethical issues underlying the application of genetic technologies to human beings. Probing the implications of the remarkable advances in genetics, the authors ask how should these affect our understanding of distributive justice, equality of opportunity, the rights and obligations as parents, the meaning of disability, and the role of the concept of human nature in ethical theory and practice. The book offers a historical context to contemporary debate over the use of these technologies by examining the eugenics movement of the late nineteenth and early twentieth centuries. The questions raised in this book will be of interest to any reflective reader concerned about science and society and the rapid development of biotechnology, as well as to professionals in such areas as philosophy, bioethics, medical ethics, health management, law, and political science.
Theoretical issues in b physics

Examples are given of some current questions in b physics to which LHC experiments may provide answers. These include (i) the precise determination of parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix; (ii) measurements of CKM phases using B decays to CP eigenstates; (iii) the search for direct CP asymmetries in B decays; (iv) rare radiative B decays; (v) the study of B s properties and decays, (vi) excited states of B and B s mesons, and (vii) the search for heavier quarks which could mix with the b quark. PACS: 11.30.Er – 11.30.Hv – 13.25.Hw – 14.40.Nd
The highest energy neutrinos

Measurements of the arrival directions of cosmic rays have not revealed their sources. High energy neutrino telescopes attempt to resolve the problem by detecting neutrinos whose directions have not been scrambled by magnetic fields. The key issue is whether the neutrino flux produced in cosmic ray accelerators is detectable. It is believed that the answer is affirmative, both for the galactic and extragalactic sources, provided the detector has kilometer-scale dimensions. We revisit the case for kilometer-scale neutrino detectors in a model-independent way by focussing on the energetics of the sources. The real breakthrough though has not been on the theory but on the technology front: the considerable technical hurdles to build such detectors have been overcome.
Passive Fuel-Air Mixing and Emissions Control Via Lobed Injectors

This experimental study examined the effects of differing levels of passive fuel-air premixing on flame structures and their associated NO x and CO emissions. Four alternative fuel injector geometries were explored, three of which had lobed shapes. Prior experimental studies of two of these lobed injector flowfields focused on nonreactive mixing characteristics (Smith, L. L., Majamaki, A. J., Lam, I. T., Delabroy, O., Karagozian, A. R., Marble, F. E., and Smith, O. I., Mixing Enhancement in a Lobed Injector, Physics of Fluids, Vol. 9, No. 3, 1997, pp. 667-678) and emissions measurements in the absence of air confinement [Mitchell, M. G., Smith, L. L., Karagozian, A. R., and Smith, O.I., Burner Emissions Associated with Lobed and Non-Lobed Fuel Injectors, Twenty-Seventh Symposium (International) on Combustion, The Combustion Inst., Pittsburgh, PA, 1998, pp. 1825-1831]. The present studies examined the effects of confinement of the crossflow to reduce the local equivalence ratio as well as the effects of altering the geometry and position of the flameholders to further influence passive fuel-air premixing. NO x and CO emissions as well as flame photographs and planar laser-induced fluorescence imaging of seeded acetone were used to characterize injector performance and fuel and flame evolution. It was found that, with significant air confinement, forcing a more intimate mixing between fuel and air before ignition and flameholding, both NO x and CO emissions could be simultaneously reduced under the same operating conditions via this passive flow control technique.
The Littlest Higgs

We present an economical theory of natural electroweak symmetry breaking, generalizing an approach based on deconstruction. This theory is the smallest extension of the Standard Model to date that stabilizes the electroweak scale with a naturally light Higgs and weakly coupled new physics at TeV energies. The Higgs is one of a set of pseudo Goldstone bosons in an SU(5)/SO(5) nonlinear sigma model. The symmetry breaking scale f is around a TeV, with the cutoff Λ4πf ~ 10 TeV. A single electroweak doublet, the `little Higgs', is automatically much lighter than the other pseudo Goldstone bosons. The quartic self-coupling for the little Higgs is generated by the gauge and Yukawa interactions with a natural size (g2, λt2), while the top Yukawa coupling generates a negative mass squared triggering electroweak symmetry breaking. Beneath the TeV scale the effective theory is simply the minimal Standard Model. The new particle content at TeV energies consists of one set of spin one bosons with the same quantum numbers as the electroweak gauge bosons, an electroweak singlet quark with charge 2/3, and an electroweak triplet scalar. One loop quadratically divergent corrections to the Higgs mass are cancelled by interactions with these additional particles.
Inhomogeneous maps and mathematical theory of selection

In this paper we develop a theory of general selection systems with discrete time and explore the evolution of selection systems, in particular, inhomogeneous populations. We show that the knowledge of the initial distribution of the selection system allows us to determine explicitly the system distribution at the entire time interval. All statistical characteristics of interest, such as mean values of the fitness or any trait can be predicted effectively for indefinite time and these predictions dramatically depend on the initial distribution. The Fisher Fundamental theorem of natural selection (FTNS) and more general the Price equations are the famous results of the mathematical selection theory. We show that the problem of dynamic insufficiency for the Price equations and for the FTNS can be resolved within the framework of selection systems. Effective formulas for solutions of the Price equations and for the FTNS are derived. Applications of the developed theory to some other problems of mathematical ...
On A Hypergraph Turán Problem Of Frankl

Let $$C^{{{\left( {2k} \right)}}}_{r}$$ be the 2k-uniform hypergraph obtained by letting P1, . . .,Pr be pairwise disjoint sets of size k and taking as edges all sets Pi∪Pj with i ≠ j. This can be thought of as the ‘k-expansion’ of the complete graph Kr: each vertex has been replaced with a set of size k. An example of a hypergraph with vertex set V that does not contain $$C^{{{\left( {2k} \right)}}}_{3}$$ can be obtained by partitioning V = V1 ∪V2 and taking as edges all sets of size 2k that intersect each of V1 and V2 in an odd number of elements. Let $${\user1{\mathcal{B}}}^{{{\left( {2k} \right)}}}_{n}$$ denote a hypergraph on n vertices obtained by this construction that has as many edges as possible. For n sufficiently large we prove a conjecture of Frankl, which states that any hypergraph on n vertices that contains no $$C^{{{\left( {2k} \right)}}}_{3}$$ has at most as many edges as $${\user1{\mathcal{B}}}^{{{\left( {2k} \right)}}}_{n}$$.Sidorenko has given an upper bound of $$\frac{{r - 2}}{{r - 1}}$$ for the Tur´an density of $$C^{{{\left( {2k} \right)}}}_{r}$$ for any r, and a construction establishing a matching lower bound when r is of the form 2p+1. In this paper we also show that when r=2p+1, any $$C^{{{\left( 4 \right)}}}_{r}$$-free hypergraph of density $$\frac{{r - 2}}{{r - 1}} - o{\left( 1 \right)}$$ looks approximately like Sidorenko’s construction. On the other hand, when r is not of this form, we show that corresponding constructions do not exist and improve the upper bound on the Turan density of $$C^{{{\left( 4 \right)}}}_{r}$$ to $$\frac{{r - 2}}{{r - 1}} - c{\left( r \right)}$$, where c(r) is a constant depending only on r.The backbone of our arguments is a strategy of first proving approximate structure theorems, and then showing that any imperfections in the structure must lead to a suboptimal configuration. The tools for its realisation draw on extremal graph theory, linear algebra, the Kruskal–Katona theorem and properties of Krawtchouck polynomials.
An Improved Streamline-Generating Technique That Uses the Boundary (Integral) Element Method

The boundary element method (BEM) has been used to generate streamlines for homogeneous and sectionally homogeneous reservoirs having irregular boundaries. This technique is superior to earlier methods that use ''image wells'' to simulate the reservoir boundary, especially for cases where the reservoir boundary is irregularly shaped. It has wider applicability to different kinds of reservoirs and eliminates the need for trial-and-error solutions. The errors caused by discretization and numerical approximation arise on and adjacent to the boundaries only, therefore the pressures and pressure gradients on which the streamlines are derived can be calculated with very high accuracy in the interior of the reservoir. Thus, the streamlines generated with this method are expected to be more realistic and representative of the actual physical system.
Therapy of cutaneous lupus erythematosus

: Patients with cutaneous lesions of lupus erythematosus (LE) can generally be managed with standard therapies. The patient should have a firmly established diagnosis. Evaluation will allow the treating physician to assign a prognosis. Patients with discoid LE and subacute cutaneous LE are generally photosensitive and therefore sunscreens, protective clothing, and behavioral alteration should be discussed with all patients. Topical corticosteroids are a standard form of therapy, but “newer” agents such as retinoids, calcipotriene, and tacrolimus might be effective. Antimalarial agents are generally effective. Attempts to reduce or stop smoking may aid in the control of cutaneous LE (CLE). The choice of alternative therapy is personal and discussions of the risks and benefits should be carefully documented. Successful therapy for CLE is possible in almost all well-motivated, cooperative patients.
The Casimir effect: recent controversies and progress

The phenomena implied by the existence of quantum vacuum fluctuations, grouped under the title of the Casimir effect, are reviewed, with emphasis on new results discovered in the past four years. The Casimir force between parallel plates is rederived as the strong-coupling limit of δ-function potential planes. The role of surface divergences is clarified. A summary of effects relevant to measurements of the Casimir force between real materials is given, starting from a geometrical optics derivation of the Lifshitz formula, and including a rederivation of the Casimir–Polder forces. A great deal of attention is given to the recent controversy concerning temperature corrections to the Casimir force between real metal surfaces. A summary of new improvements to the proximity force approximation is given, followed by a synopsis of the current experimental situation. New results on Casimir self-stress are reported, again based on δ-function potentials. Progress in understanding divergences in the self-stress of dielectric bodies is described, in particular the status of a continuing calculation of the self-stress of a dielectric cylinder. Casimir effects for solitons, and the status of the so-called dynamical Casimir effect, are summarized. The possibilities of understanding dark energy, strongly constrained by both cosmological and terrestrial experiments, in terms of quantum fluctuations are discussed. Throughout, the centrality of quantum vacuum energy in fundamental physics is emphasized.
Crystal structure and morphology control of molybdenum carbide nanomaterials synthesized from an amine–metal oxide composite

Multiple phases of molybdenum carbide have been synthesized using a unique amine-metal oxide composite material. By combining molybdenum oxide and an amine, a templated precursor is formed which can be thermally decomposed to form molybdenum carbide with control over the structure and morphology of the nano-sized products.
THE SEARCH FOR DARK MATTER FROM SPACE AND ON THE EARTH

We first show that the MOND concept is very unlikely: nonbaryonic dark matter exists. We then discuss dwarf special galaxies that in some cases appear to be nearly pure dark matter systems. The search for dark matter particles can be carried out from space (sterile neutrinos neutralino annihilation) or on the Earth (direct detection). We describe progress in these areas and focus on the progress of the ZEPLIN II detector now taking data.1,2.
Non-isotopic Heegaard splittings of Seifert fibered spaces

We find a geometric invariant of isotopy classes of strongly irreducible Heegaard splittings of toroidal 3‐manifolds. Combining this invariant with a theorem of R Weidmann, proved here in the appendix, we show that a closed, totally orientable Seifert fibered space M has infinitely many isotopy classes of Heegaard splittings of the same genus if and only if M has an irreducible, horizontal Heegaard splitting, has a base orbifold of positive genus, and is not a circle bundle. This characterizes precisely which Seifert fibered spaces satisfy the converse of Waldhausen’s conjecture. 57M27; 57N10, 57M60
WEAKLY DAMPED MODES IN STAR-CLUSTERS AND GALAXIES

A perturber may excite a coherent mode in a star cluster or galaxy. If the stellar system is stable, it is commonly assumed that such a mode will be strongly damped and therefore of little practical consequence other than redistributing momentum and energy deposited by the perturber. This paper demonstrates that this assumption is false; weakly damped modes exist and may persist long enough to have observable consequences. To do this, a method for investigating the dispersion relation for spherical stellar systems and for locating weakly damped modes in particular is developed and applied to King models of varying concentration. This leads to a following remarkable result: King models exhibit very weakly damped m = 1 modes over a wide range of concentration (0.67 less than or equal to c less than or equal to 1.5 have been examined). The predicted damping time is tens of hundreds of crossing times. This mode causes the peak density to shift from and slowly revolve about the initial center. The existence of the mode is supported by n-body simulation. Higher order modes and possible astronomical consequences are discussed. Weakly damped modes, for example, may provide a neutral explanation for observed discrepancies between density and kinematic centers in galaxies, off-center nuclei, the location of velocity cusps due to massive black holes, and both m = 1 and barlike disturbances of disks enbedded in massive halos or spheroids. Gravitational shocking may excite the m = 1 mode in globular clusters, which could modify their subsequent evolution and displace the positions of exotic remnants.
Afterpulse Time Spectrum Measurement of RCA 8850 Photomultiplier

The photomultiplier dark pulse-height, signal induced pulse-height, and afterpulse time spectra have been measured on three RCA 8850 52 mm-diameter photomultipliers. The first dynode of this photomultiplier has a cesium activated, gallium-phosphide secondary emitting surface. Measurement techniques and the measuring systems are described in detail.
Social and ethical considerations in virtual worlds

Purpose – The computer has evolved from a tool used solely for business, research and governmental purposes to an instrument characterized by social interaction in virtual worlds. In this context, like‐minded people can converse and interact online in ways that are both enjoyable and satisfying. However, virtual worlds also bring with them cause for concern. These concerns include – but are not limited to – the loss of one's privacy, the fear of being exploited, and the loss of identity. This paper seeks to investigate the current state of affairs of online virtual worlds in terms of what many people deem acceptable and unacceptable forms of behavior.Design/methodology/approach – A study is presented that explores the unmonitored distribution of electronic materials through the internet. Available technologies are surveyed and recommendations made based on these analyses.Findings – This paper has shown that effective enforcement of online behavior is, at least, a very complicated undertaking – not one tha...
Mild reductive opening of aryl pyranosides promoted by scandium(III) triflate.

An efficient method for the nucleophilic ring opening of stereochemically well-defined aryl pyranosides is described. The reaction effects a formal deoxygenation of the benzylic position to provide useful, enantioenriched building blocks. To illustrate the utility of the Sc(OTf)3-promoted ring opening, a short synthesis of the C11−C21 fragment of reblastatin and geldanamycin is described.