cssi/SciSciGPT-SciSciNet huggingface dataset:
Solitary waves under the influence of a long-wave mode

Abstract The dynamics of solitons of the nonlinear Schrodinger equation under the influence of dissipative and dispersive perturbations is investigated. In particular a coupling to a long-wave mode is considered using extended Ginzburg-Landau equations. The study is motivated by the experimental observation of localized wave trains (‘pulses’) in binary-liquid convection. These pulses have been found to drift exceedingly slowly. The perturbation analysis reveals two distinct mechanisms which can lead to a ‘trapping’ of the pulses by the long-wave concentration mode. They are given by the effect of the concentration mode on the local growth rate and on the frequency of the wave. The latter, dispersive mechanism has not been recognized previously, despite the fact that it dominates over the dissipative contribution within the perturbation theory. A second un-expected result is that the pulse can be accelerated by the concentration mode despite the reduced growth rate ahead of the pulse. The dependence of the pulse velocity on the Rayleigh number is discussed, and the hysteretic ‘trapping’ transitions suggested by the perturbation theory are confirmed by numerical simulations, which also reveal oscillatory behavior of the pulse velocity in the vicinity of the transition. The derivation and reconstitution of the extended Ginzburg-Landau equations is discussed in detail.
Program control via transition matrices: a novel application of micro-programming

The problem of processing and interpreting character-strings in a systematic, efficiently implementable manner has given rise to a variety of decision-(or transition-) table and transition-diagram techniques. These have been used in the design and/or coding of string-oriented processors, such as lexical analysis protions of compilers. All these techniques share in common the idea of an input driven transition control.This report describes a micro-coded implementation fo a particularly rich concept--the transition matrix (TM). The micro-coded interpreter (ITM) executes the flow-of-control implicit within the structure of the TM. The TM may be coded in a natural, easy to use language (LTMφSP), and then be automatically translated into ITM-usable form by a user-level translator called TMφSP. The completed system (ITM and TMφSP) permits TM-oriented decision-making techniques to be utilized in virtually any task that can be described by means of transition matrix.
Biosynthesis of (+)-epicubenol

Abstract Incubation of [6-2H]FPP (14a) with epicubenol synthase isolated from Streptomyces sp. LL-B7 gave epicubenol (1c) labeled at D-9 as established by 2H NMR. These results confirm the involvement of a predicted 1,2-hydride shift in the mechanism of formation of 1.
The normality of digits in almost constant additive functions

We consider numbers formed by concatenating some of the base \(b\) digits from additive functions \(f(n)\) that closely resemble the prime divisor counting function \(\Omega (n)\). If we concatenate the last $$\begin{aligned} \left\lceil y \frac{\log \log \log n }{\log b} \right\rceil \end{aligned}$$ digits of each \(f(n)\) in succession, then the number so created will be normal if and only if \(0 < y \le 1/2\). This provides insight into the randomness of digit patterns of additive functions after the Erdős-Kac theorem becomes ineffective.
Perturbation analysis and optimization of queueing networks

A new time-domain-based approach is developed in this paper for the perturbation analysis of queueing networks. We show that, by observing a single sample path realization of the network trajectory, we can derive sensitivity information of the throughput of the system with respect to various parameters. This information can then be used for the optimization of queueing networks. Numerous experiments as well as analytical results demonstrating the validity of this new approach are given and discussed.
Precise vacuum stability bound in the standard model

Abstract In the standard model, a lower bound to the Higgs mass (for a given top quark mass) exists if one requires that the standard model vacuum be stable. This bound is calculated as precisely as possible, including the most recent values of the strong and electroweak couplings, corrected two-loop beta functions and radiative corrections to the Higgs and top quark masses. In addition to being somewhat more precise, this work differs from previous calculations in that the bounds are given in terms of the poles of the Higgs and top quark propagators, rather than, for example, the “ MS top quark mass”. This difference can be as large as 6–10 GeV for the top quark mass, which corresponds to as much as 15 GeV for the lower bound to the Higgs mass. I concentrate on top quark masses between 130 and 150 GeV, and for α s ( M z )=0.117 find that (over that range) m H >75 GeV +1.64( m t -140 GeV). This result increases (decreases) by 3 GeV if the strong coupling decreases (increases) by 0.007, and is accurate to 1 GeV in m t and 2 GeV in m H . If one allows for the standard model vacuum to be unstable, then weaker bounds can be obtained - these are also discussed.
SAKE: Software attestation for key establishment in sensor networks

This paper presents a protocol called Software Attestation for Key Establishment (SAKE), for establishing a shared key between any two neighboring nodes of a sensor network. SAKE guarantees the secrecy and authenticity of the key that is established, without requiring any prior authentic or secret cryptographic information in either node. In other words, the attacker can read and modify the entire memory contents of both nodes before SAKE executes. Further, to the best of our knowledge, SAKE is the only protocol that can perform key re-establishment after sensor nodes are compromised, because the presence of the attacker's code in the memory of either protocol participant does not compromise the security of SAKE. Also, the attacker can perform any active or passive attack using an arbitrary number of malicious, colluding nodes. SAKE does not require any hardware modification to the sensor nodes, human mediation, or secure side channels. However, we do assume the setting of a computationally-limited attacker that does not introduce its own computationally-powerful nodes into the sensor network. SAKE is based on Indisputable Code Execution (ICE), a primitive we introduce in previous work to dynamically establish a trusted execution environment on a remote, untrusted sensor node.
Prevention of adhesion formation after radical oophorectomy using a sodium hyaluronate-carboxymethylcellulose (HA-CMC) barrier.

Abstract Objectives. To evaluate the efficacy of a hyaluronate-carboxymethylcellulose (HA-CMC) barrier for prevention of pelvic adhesion formation in women undergoing primary cytoreductive surgery with radical oophorectomy for locally advanced epithelial cancer. Methods. Between 3/1/01 and 3/1/02, all patients undergoing primary surgery for locally advanced FIGO Stage III–IV epithelial ovarian cancer were prospectively offered study enrollment. Radical oophorectomy (en bloc rectosigmoid colectomy) with total pelvic peritonectomy was performed as clinically indicated. Intestinal continuity was reestablished via stapled anastomosis following complete cytoreduction of pelvic disease. The entire pelvic peritoneal defect was covered with subdivided sheets of HA-CMC (6.5 cm × 5.0 cm) using a ‘quilting' technique. The abdominal wall incision site was not treated with adhesion preventive measures. At second-look surgery, four-quadrant pelvic (treated area) and abdominal wall (untreated internal control) adhesion scores were assigned using a previously validated scoring system. Statistical analysis for differences in mean pelvic and abdominal wall adhesion scores was performed using Student's t test. Results. Fourteen patients satisfied all inclusion criteria. Abdominal wall adhesions were noted in 92.9% of patients. In the pelvis, the dorsal peritoneal surfaces were the most common sites of adhesion formation (42.9%). Overall, the mean pelvic (treated) adhesion score was statistically significantly lower (0.91, SD ± 1.04) than the mean abdominal wall (untreated control) score (5.56, SD ± 4.55, P = 0.02). There were no instances of intestinal anastomotic leak, and no peri-operative complications directly attributable to HA-CMC were observed. Conclusions. Placement of a HA-CMC barrier is associated with a significant reduction in the extent and density of pelvic adhesion formation following radical oophorectomy and pelvic peritonectomy for locally advanced epithelial ovarian cancer.
Monetary policy games, inflationary bias, and openness

Abstract When a country's central bank has higher output objectives than those of wage-setters, the noncooperative Nash equilibrium contains an inflationary bias, which is higher, the flatter the economy's aggregate supply curve. An economy's openness from the input side is an exogenous observable characteristic that provides a direct way of testing the theory. When the imported intermediate goods displace capital (labor) in production, a higher degree of openness flattens (steepens) the economy's aggregate supply curve and increases (decreases) the inflationary bias.
Sexual dimorphism in epigenomic responses of stem cells to extreme fetal growth

Extreme fetal growth is associated with increased susceptibility to a range of adult diseases through an unknown mechanism of cellular memory. We tested whether heritable epigenetic processes in long-lived CD34(+) haematopoietic stem/progenitor cells showed evidence for re-programming associated with the extremes of fetal growth. Here we show that both fetal growth restriction and over-growth are associated with global shifts towards DNA hypermethylation, targeting cis-regulatory elements in proximity to genes involved in glucose homeostasis and stem cell function. We find a sexually dimorphic response; intrauterine growth restriction is associated with substantially greater epigenetic dysregulation in males, whereas large for gestational age growth predominantly affects females. The findings are consistent with extreme fetal growth interacting with variable fetal susceptibility to influence cellular ageing and metabolic characteristics through epigenetic mechanisms, potentially generating biomarkers that could identify infants at higher risk for chronic disease later in life.
The epigenetics of epithelial-mesenchymal plasticity in cancer.

Epithelial-mesenchymal transitions (EMTs) are a key requirement for cancer cells to metastasize and colonize in a new environment. Epithelial-mesenchymal plasticity is mediated by master transcription factors and is also subject to complex epigenetic regulation. This Review outlines our current understanding of the interactions between EMT-inducing transcription factors and epigenetic modulators during cancer progression and the therapeutic implications of exploiting this intricate regulatory process. During the course of malignant cancer progression, neoplastic cells undergo dynamic and reversible transitions between multiple phenotypic states, the extremes of which are defined by the expression of epithelial and mesenchymal phenotypes. This plasticity is enabled by underlying shifts in epigenetic regulation. A small cohort of pleiotropically acting transcription factors is widely recognized to effect these shifts by controlling the expression of a constituency of key target genes. These master regulators depend on complex epigenetic regulatory mechanisms, notably the induction of changes in the modifications of chromatin-associated histones, in order to achieve the widespread changes in gene expression observed during epithelial-mesenchymal transitions (EMTs). These associations indicate that an understanding of the functional interactions between such EMT-inducing transcription factors and the modulators of chromatin configuration will provide crucial insights into the fundamental mechanisms underlying cancer progression and may, in the longer term, generate new diagnostic and therapeutic modalities for treating high-grade malignancies.
ON THE COST OF NEW ISSUES OF COMMON STOCK: AN AMENDMENT TO THE CONSTANT GROWTH MODEL

Expansion decisions by corporate managements are importantly influenced by their perceptions of the firm's cost of capital and especially the cost of common equity. Their decision making is then influenced by the common perception that new issues of common stock are more costly than retained earnings because of the flotation costs inherent in new issues. Thus a rate of expansion that requires new issues is downgraded in decision making. In this paper the authors show that in actuality new issues of common equity may be less costly than retained earnings. Thus different decision-making implications are clearly involved.
Respondable risk and incentives for CEOs: The role of information-collection and decision-making

Abstract This paper examines the incentive provision when the agent can respond to risk by exerting effort to collect information about the underlying state and making corresponding decisions. Such effort is shown to be more valuable in a riskier environment and incentives can increase with “respondable” risk. The relation between incentives and risk is more positive when the agent's effort is more effective in collecting information or in acting upon it. Using data on chief executive officers (CEOs), I find that incentives for CEOs increase with industry-wide risk, a measure of respondable risk. The positive relation diminishes when the CEO is less able to collect information or is less effective in acting upon it.
Probably Almost Discriminative Learning

This paper develops a new computational model for learning stochastic rules, called PAD (Probably Almost Discriminative)-learning model, based on statistical hypothesis testing theory. The model deals with the problem of designing a discrimination algorithm to test whether or not any given test sequence of examples of pairs of (instance, label) has come from a given stochastic rule P*. Here a composite hypothesis {\tilde P} is unknown other than it belongs to a given class {\cal C}. In this model, we propose a new discrimination algorithm on the basis of the MDL (Minimum Description Length) principle, and then derive upper bounds on the least test sample size required by the algorithm to guarantee that two types of error probabilities are respectively less than δ1 and δ2 provided that the distance between the two rules to be discriminated is not less than e. For the parametric case where {\cal C} is a parametric class, this paper shows that an upper bound on test sample size is given by O({1\over \varepsilon}\ {\rm ln}\ {1\over\delta _1}\ +\ {1\over \varepsilon ^2}\ {\rm ln}{1\over \delta _2}\ +\ {\tilde{k}\over \varepsilon}\ {\rm ln}\ {\tilde{k}\over \varepsilon}\ +\ {\ell({\tilde M})\over \varepsilon}). Here {\tilde k} is the number of real-valued parameters for the composite hypothesis {\tilde P,} and \ell({\tilde M}) is the description length for the countable model for {\tilde P.} Further this paper shows that the MDL-based discrimination algorithm performs well in the sense of sample complexity efficiency, comparing it with other kinds of information-criteria-based discrimination algorithms. This paper also shows how to transform any stochastic PAC (Probably Approximately Correct)-learning algorithm into a PAD-learning algorithm. For the non-parametric case where {\cal C} is a non-parametric class but the discrimination algorithm uses a parametric class, this paper demonstrates that the sample complexity bound for the MDL-based discrimination algorithm is essentially related to Barron and Cover's index of resolvability. The sample complexity bound gives a new view at the relationship between the index of resolvability and the MDL principle from the PAD-learning viewpoint.
Driver Turn-Taking Behavior in Congested Freeway Merges

Data from four merge locations in northern California and Toronto, Ontario, Canada, unveil a notable feature of driver turn taking. It was observed that queued vehicles from the on-ramp and freeway traffic streams entered a congested merge in some (nearly) fixed ratio that was independent of the merge outflow. Drivers in competing traffic streams thus entered the merge by adopting some definite turn-taking behavior, and this behavior was not influenced by the severity of the exogenous flow restriction from downstream. The findings validate part of an existing theory of merging traffic and should be considered when any new such theories are developed.
Early detection of cancer by regression analysis and computer simulation of gene regulatory rules

Cellular signaling and dynamic interaction among genes result in stable phenotype structures such as tumor or non tumor cells. Tumor and non-tumor cellular cells often contain some identical cancer causing genes but due to differences in their regulatory networks they evolve differently. As a result, if such regulatory networks are discovered one could predict whether a cell containing particular cancer genes will in fact end up to become a cancerous cell. This paper utilizes a mathematical approach to determine such regulatory rules for a set of cells containing cancer causing genes and uses computer simulation to predict whether in a long run a particular cell will evolve into a cancerous cell. The proposed process utilizes Probabilistic Boolean Networks (PBN) on two gene regulatory networks; one for tumor and one for non-tumor producing structures. The process uses a regression analysis to identify the regulatory networks and a computer simulation model to predict long term cancer potential.
Mechanistic investigation of UDP-galactopyranose mutase from Escherichia coli using 2- and 3-fluorinated UDP-galactofuranose as probes.

The galactofuranose moiety found in many surface constituents of microorganisms is derived from UDP-d-galactopyranose (UDP-Galp) via a unique ring contraction reaction catalyzed by UDP-Galp mutase. This enzyme, which has been isolated from several bacterial sources, is a flavoprotein. To study this catalysis, the cloned Escherichia coli mutase was purified and two fluorinated analogues, UDP-[2-F]Galf (9) and UDP-[3-F]Galf (10), were chemically synthesized. These two compounds were found to be substrates for the reduced UDP-Galp mutase with the Km values determined to be 65 and 861 μM for 9 and 10, respectively, and the corresponding kcat values estimated to be 0.033 and 5.7 s-1. Since the fluorine substituent is redox inert, a mechanism initiated by the oxidation of 2-OH or 3-OH on the galactose moiety can thus be firmly ruled out. Furthermore, both 9 and 10 are poorer substrates than UDP-Galf, and the rate reduction for 9 is especially significant. This finding may be ascribed to the inductive effect of ...
Fourier domain preconditioned conjugate gradient algorithm for atmospheric tomography

By 'atmospheric tomography' we mean the estimation of a layered atmospheric turbulence profile from measurements of the pupil-plane phase (or phase gradients) corresponding to several different guide star directions. We introduce what we believe to be a new Fourier domain preconditioned conjugate gradient (FD-PCG) algorithm for atmospheric tomography, and we compare its performance against an existing multigrid preconditioned conjugate gradient (MG-PCG) approach. Numerical results indicate that on conventional serial computers, FD-PCG is as accurate and robust as MG-PCG, but it is from one to two orders of magnitude faster for atmospheric tomography on 30 m class telescopes. Simulations are carried out for both natural guide stars and for a combination of finite-altitude laser guide stars and natural guide stars to resolve tip-tilt uncertainty.
Balanced realizations of singularly perturbed systems

Abstract Balanced realizations of linear time-invariant singularly perturbed systems are studied. The reduced model of a singularly perturbed system that is obtained, based on the balanced realization, is compared to that obtained by time-scale considerations. An approximate balancing transformation for singularly perturbed systems is constructed based on balancing transformations of the approximating slow and fast subsystems.
Group symmetry and covariance regularization

Statistical models that possess symmetry arise in diverse settings such as random fields associated to geophysical phenomena, exchangeable processes in Bayesian statistics, and cyclostationary processes in engineering. We formalize the notion of a symmetric model via group invariance. We propose projection onto a group fixed point subspace as a fundamental way of regularizing covariance matrices in the high-dimensional regime. In terms of parameters associated to the group we derive precise rates of convergence of the regularized covariance matrix and demonstrate that significant statistical gains may be expected in terms of the sample complexity.
Properties of O VI Absorption in the Local Interstellar Medium

The measurement of absorption over short distances in the local interstellar medium (LISM) provides an excellent opportunity to study the properties of O VI absorption and its kinematic relationship to absorption by tracers of cool and warm gas. We report on the properties of LISM O VI absorption observed with 20 km s-1 resolution Far Ultraviolet Spectroscopic Explorer (FUSE) observations of 39 white dwarfs (WDs) ranging in distance from 37 to 230 pc with a median distance of 109 pc. LISM O VI is detected with ≥2 σ significance along 24 of 39 lines of sight. The column densities range from log N(O ) = 12.38 to 13.60 with a median value of 13.10. The line-of-sight volume density, n(O ) = N(O )/d, exhibits a large dispersion ranging from 0.68 × 10-8 to 13.0 × 10-8 cm-3 with an average value n(O ) = 3.6 × 10-8 cm-3 twice larger than that found for more distant sight lines in the Galactic disk. The Doppler parameter, b, for the ≥4 σ O VI detections ranges from 15.0 ± 3.5 to 36.2 ± 7.3 km s-1, with average and dispersion of 23.0 ± 5.6 km s-1. The narrowest profiles are consistent with thermal Doppler broadening of O VI near its temperature of peak abundance, 2.8 × 105 K. log N(O ) is observed to correlate with b. The broader profiles are tracing a combination of O VI with T > 2.8 × 105 K, multiple component O VI absorption either in interfaces or hot bubbles, and/or the evaporative outflow of conductive interface gas. Comparison of the average velocities of O VI and C II absorption reveals 10 cases where the O VI absorption is closely aligned with the C II absorption as expected if the O VI is formed in a condensing interface between the cool and warm absorption traced by C II (and also O I and C III) and a hot exterior gas. The comparison also reveals 13 cases where O VI absorption is displaced to positive velocity by 7-29 km s-1 from the average velocity of C II. The positive velocity O VI is mostly found in the north Galactic hemisphere. The positive-velocity O VI appears to be tracing the evaporative flow of O VI from a young interface between warm gas and a hot exterior medium. However, it is possible that the positive-velocity O VI is instead tracing cooling hot Local Bubble gas. The properties of the O VI absorption in the LISM are broadly consistent with the expectations of the theory of conductive interfaces caught in the old condensing phase and possibly in the young evaporative phase of their evolution.
A generalization of plexes of Latin squares

A k-plex of a Latin square is a collection of cells representing each row, column, and symbol precisely k times. The classic case of k=1 is more commonly known as a transversal. We introduce the concept of a k-weight, an integral weight function on the cells of a Latin square whose row, column, and symbol sums are all k. We then show that several non-existence results about k-plexes can been seen as more general facts about k-weights and that the weight analogues of several well-known existence conjectures for plexes actually hold for k-weights.
Does Focus Really Matter? Specialized vs. Diversified REITs

REITs that limit their holdings to a single property type typically defend their lack of diversification by claiming the management possesses special investment expertise in that particular property type. This paper investigates whether property type specialized REITs outperform diversified REITs thus providing evidence of superior management expertise associated with specialized REITs. We compare the performance of specialized versus diversified REIT portfolios during 1997–2006 by examining abnormal returns using CAPM and the Fama-French three factor model with momentum. We find no evidence of superior performance associated with REITs specializing in a single property type. On the contrary, diversified REITs somewhat outperform specialized REITs, but not by a statistically significant margin. Also, consistent with theory, we find that specialized REITs have higher market risk than diversified REITs.
Spectropolarimetry of the Classical T Tauri Star TW Hydrae

We present high-resolution (R ≈ 60,000) circular spectropolarimetry of the classical T Tauri star TW Hydrae. We analyze 12 photospheric absorption lines and measure the net longitudinal magnetic field for six consecutive nights. While no net polarization is detected the first five nights, a significant photospheric field of Bz = 149 ± 33 G is found on the sixth night. To rule out spurious instrumental polarization, we apply the same analysis technique to several nonmagnetic telluric lines, detecting no significant polarization. We further demonstrate the reality of this field detection by showing that the splitting between right and left polarized components in these 12 photospheric lines shows a linear trend with Lande g-factor times wavelength squared, as predicted by the Zeeman effect. However, this longitudinal field detection is still much lower than that which would result if a pure dipole magnetic geometry is responsible for the mean magnetic field strength of 2.6 kG previously reported for TW Hya. We also detect strong circular polarization in the He I λ5876 and Ca II λ8498 emission lines, indicating a strong field in the line formation region of these features. The polarization of the Ca II line is substantially weaker than that of the He I line, which we interpret as being due to a larger contribution to the Ca II line from chromospheric emission in which the polarization signals cancel. However, the presence of polarization in the Ca II line indicates that accretion shocks on classical T Tauri stars do produce narrow emission features in the infrared triplet lines of calcium.
Taking into Account the Differences between Actively and Passively Acquired Data: The Case of Active Learning with Support Vector Machines for Imbalanced Datasets

Actively sampled data can have very different characteristics than passively sampled data. Therefore, it's promising to investigate using different inference procedures during AL than are used during passive learning (PL). This general idea is explored in detail for the focused case of AL with cost-weighted SVMs for imbalanced data, a situation that arises for many HLT tasks. The key idea behind the proposed InitPA method for addressing imbalance is to base cost models during AL on an estimate of overall corpus imbalance computed via a small unbiased sample rather than the imbalance in the labeled training data, which is the leading method used during PL.
Formation of a Buffer Layer for Graphene on C-Face SiC{0001}

Graphene films prepared by heating the SiC\( (000\bar{1}) \) surface (the C-face of the {0001} surface) in a Si-rich environment have been studied using low-energy electron diffraction (LEED) and low-energy electron microscopy. Upon graphitization, an interface with \( \sqrt {43} \times \sqrt {43} - R \pm 7.6^\circ \) symmetry is observed by in situ LEED. After oxidation, the interface displays \( \sqrt 3 \times \sqrt 3 - R 30^\circ \) symmetry. Electron reflectivity measurements indicate that these interface structures arise from a graphene-like “buffer layer” that forms between the graphene and the SiC, similar to that observed on Si-face SiC. From a dynamical LEED structure calculation for the oxidized C-face surface, it is found to consist of a graphene layer sitting on top of a silicate (Si2O3) layer, with the silicate layer having the well-known structure as previously studied on bare SiC\( (000\bar{1}) \) surfaces. Based on this result, the structure of the interface prior to oxidation is discussed.
Recent advances in mercury photosensitized reactions

Abstract Alkanes, alcohols, ethers, amines, and other volatile organic compounds can be dimerized in a simple reactor at room temperature and pressure and on a multigram scale by Hg photosensitization. If two different substrates are present, the products include homo- and cross-dimers in a ratio that depends on the vapor pressures and the relative bond strengths of the reactive C H bonds in each species. The Hg excited state responsible, Hg*, homolyzes C H bonds of alkanes, but appears to bind to heteroatoms, such as N, and unsaturated groups such as -CO2H. This can lead to problems in the dimerization of non-alkane substrates. In many cases, these problems can be solved by addition of H2. Reaction of H2 with Hg* gives H atoms, which now allows amines, esters, ketones, and car☐ylic acids to be dimerized. Alkenes, including unsaturated acids, esters, nitriles, epoxides, and fluoroalkenes, give H addition, and the resulting radicals dimerize. Quantitative studies allow prediction of product ratios and relative reactivities given bond strength data, or the bond strengths may be estimated from the relative reactivities. Alkanes are converted to sulfonic acids, aldehydes, ketones, and hydroperoxides by Hg photosensitization in the presence of SO2, CO, and O2.
Chemoprevention of cancer.

Chemoprevention of cancer is a means of cancer control in which the occurrence of this disease is prevented by administra tion of one or several chemical compounds. This Perspective deals with the areas in cancer control that this field addresses, the promise that it holds, and the problems that must be solved in order to realize its goals. The most desirable way of eliminating the impact of cancer in humans is by prevention. The first set of strategies for achieving this objective is to remove the causative agents. In some instances, as with cigarette smoking, it is possible to eliminate the etiological agent. However, in others it is not. The causes of most cancers in the human are not known. Under some circumstances, even when causative factors are known, neoplasia may have been initiated, and prevention now falls into the realm of suppressing the evolution of the neoplastic process. Individuals already exposed to carcinogens fall into this category as do individuals at high risk to cancer because of genetic factors. Finally, there are a considerable number of suspect carcinogens in the environment that have been identified by virtue of mutagenicity testing. Many of these mutagenic substances occur in food. The carcinogenic potential of these compounds for the human is not clear. If they do in fact play a role in the occurrence of cancer, it would be exceedingly difficult to remove them from the environment. Flavones in food are an example of a class of compounds that are mutagenic and that would be virtually impossible to remove because of their ubiqui tous distribution. Likewise, if exposure to oxygen radicals and epoxides poses a hazard, as has been suggested by some investigators, such exposures would be difficult to prevent. While removal of causative agents is the primary goal of cancer pre vention, for the foreseeable future it is likely to be incomplete. Accordingly, the development of a second line of prevention based on Chemoprevention assumes considerable importance. The human constituencies that would be the target for Chemoprevention vary. Two extremes are apparent, but in all likelihood a continuum exists between them. At one extreme are individuals at very high risk of developing cancer because of genetic predisposition or exposure to carcinogens. At the other end of the risk spectrum are individuals lacking any evidence of an increase in risk factors. The strategies for dealing with groups at varying risks differ. As the risk for developing cancer increases, the compounds likely to be most effective are those that sup press evolution of the neoplastic process. The permissible risk of toxicity from the chemopreventive agent also will increase. In contrast, when one considers chemopreventive agents to be directed at populations with no enhanced risk from cancer, protection against attack from compounds that are involved in the causation of cancer assumes a greater importance. For this
Meta-B-entacenes: new polycyclic aromatics incorporating two fused borepin rings

The synthesis of new boron-containing acenes (meta-B-entacenes) is reported. These compounds exhibit slightly non-planar core geometries with blue-shifted spectral properties and more negative electrochemical reduction potentials relative to known para isomers. Polarizable π-extended architectures were realized via cross-coupling procedures with chloro-functionalized precursors.
Electronic, magnetic and transport properties of rare-earth monopnictides

The electronic structures and magnetic properties of many rare-earth monopnictides are reviewed in this article. Possible candidate materials for spintronics devices from the rare-earth monopnictide family, i.e. high polarization (nominally half-metallic) ferromagnets and antiferromagnets, are identified. We attempt to provide a unified picture of the electronic properties of these strongly correlated systems. The relative merits of several ab initio theoretical methods, useful in the study of the rare-earth monopnictides, are discussed. We present our current understanding of the possible half-metallicity, semiconductor-metal transitions, and magnetic orderings in the rare-earth monopnictides. Finally, we propose some potential strategies to improve the magnetic and electronic properties of these candidate materials for spintronics devices.
Relativized polynomial time hierarchies having exactly K levels

It is proved that for every integer $k \geqq 0$, there is an oracle $A_k $ relative to which the polynomial time hierarchy collapses so that it has exactly k levels. Furthermore, sets $B_k $ and $C_k $ may be constructed so that, relative to $B_k $, the polynomial time hierarchy has exactly k levels and the class PSPACE coincides with the polynomial time hierarchy, and, relative to $C_k $, the polynomial time hierarchy has exactly k levels and the class PSPACE is different from the polynomial time hierarchy.
DISK-LOSS AND DISK-RENEWAL PHASES IN CLASSICAL Be STARS. I. ANALYSIS OF LONG-TERM SPECTROPOLARIMETRIC DATA

Classical Be stars are known to occasionally transition from having a gaseous circumstellar disk ('Be phase') to a state in which all observational evidence for the presence of these disks disappears ('normal B-star phase'). We present one of the most comprehensive spectropolarimetric views to date of such a transition for two Be stars, pi Aquarii and 60 Cygni.The disk-loss episode of 60 Cyg was characterized by a generally monotonic decrease in emission strength over a timescale of approx1000 days from the maximum V-band polarization to the minimum Halpha equivalent width, consistent with the viscous timescale of the disk, assuming alphaapprox0.14. pi Aqr's disk loss was episodic in nature and occurred over a timescale of approx2440 days. An observed time lag between the behavior of the polarization and Halpha in both stars indicates the disk clearing proceeded in an 'inside-out' manner. We determine the position angle of the intrinsic polarization to be 166.{sup 0}7 +- 0.{sup 0}1 for pi Aqr and 107.{sup 0}7 +- 0.{sup 0}4 for 60 Cyg, and model the wavelength dependence of the observed polarization during the quiescent diskless phase of each star to determine the interstellar polarization along the line of sight. Minor outbursts observed during themore » quiescent phase of each star shared similar lifetimes as those previously reported for mu Cen, suggesting that the outbursts represent the injection and subsequent viscous dissipation of individual blobs of material into the inner circumstellar environments of these stars. We also observe deviations from the mean intrinsic polarization position angle during polarization outbursts in each star, indicating deviations from axisymmetry. We propose that these deviations might be indicative of the injection (and subsequent circularization) of new blobs into the inner disk, either in the plane of the bulk of the disk material or in a slightly inclined (non-coplanar) orbit.« less
Gravitational Lensing by a Massive Black Hole at the Galactic Center

The manifestations of gravitational lensing by a massive black hole at the Galactic center, with particular attention given to lensing of stars in the stellar cluster that lie behind Sgr A*, and of Sgr A east, a nonthermal extended radio source which is known with certainty to lie behind the Galactic center. Lensing of the stellar cluster produces a deficit of stellar images within 10 mas of the center, and a surplus between 30 and 300 mas. The results suggest that the proper motion of the stars will produce brightness variations of stellar images on a time scale of a few years or less. Both images of such a source should be visible, and will rise and fall in luminosity together.
High quantum yield blue emission from water-soluble Au8 nanodots

Prepared within biocompatible poly(amidoamine) dendrimer hosts, blue emitting Au8 nanodots were prepared with fluorescence quantum yields more than 100 times larger than any previously prepared. The strong size-dependent blue emission from these from monodisperse Au8 nanodots was measured to be 41% in aqueous solution and 52% in methanol. These easily prepared, water-soluble, and high quantum yield gold nanodots lend insight into the molecular nature of small metal nanoclusters and may find application as novel biocompatible fluorophores.
Equivariant aspects of Yang–Mills Floer theory

Abstract We study the u-map in instanton Floer homology using Floer's exact surgery triangle. As an application we prove that the Donaldson invariants of simply-connected smooth 4-manifolds have finite type. We also construct an additive homology cobordism invariant of homology 3-spheres which is monotone with respect to definite cobordisms.
Numerical Investigation of Subsonic and Supersonic Asymmetric Vortical Flow

The high angle of attack flow about a slender body in supersonic and subsonic flow was computed for an angle of attack of 38.5 deg to study the phenomena associated with vortex asymmetry. A laminar thin-layer Navier-Stokes algorithm was used to determine whether vortex asymmetry in numerical computations is the result of a numerically induced perturbation or a property of the governing equations. The fully upwind code used in this study was symmetric in the crossflow plane to 12 orders of magnitude, the level of roundoff error on the Cray Y-MP. With a completely symmetric grid and algorithm with respect to the crossflow plane, a bump was needed to perturb the flow to asymmetry
Customizable Point-of-Interest Queries in Road Networks

We present a unified framework for dealing with exact point-of-interest (POI) queries in dynamic continental road networks within interactive applications. We show that partition-based algorithms developed for point-to-point shortest path computations can be naturally extended to handle augmented queries such as finding the closest restaurant or the best post office to stop on the way home, always ranking POIs according to a user-defined cost function. Our solution allows different trade-offs between indexing effort (time and space) and query time. Our most flexible variant allows the road network to change frequently (to account for traffic information or personalized cost functions) and the set of POIs to be specified at query time. Even in this fully dynamic scenario, our solution is fast enough for interactive applications on continental road networks.
The DEEP2 Galaxy Redshift Survey: Clustering Dependence on Galaxy Stellar Mass and Star Formation Rate at z ~ 1

We present DEEP2 galaxy clustering measurements at z {approx} 1 as a function of stellar mass, star formation rate (SFR), and specific SFR (sSFR). We find a strong positive correlation between stellar mass and clustering amplitude on 1-10 h {sup -1} Mpc scales for blue, star-forming galaxies with 9.5 < log(M{sub *}/M{sub Sun }) < 11 and no dependence for red, quiescent galaxies with 10.5 < log(M{sub *}/M{sub Sun }) < 11.5. Using recently re-calibrated DEEP2 SFRs from restframe B-band magnitude and optical colors, we find that within the blue galaxy population at z {approx} 1 the clustering amplitude increases strongly with increasing SFR and decreasing sSFR. For red galaxies there is no significant correlation between clustering amplitude and either SFR or sSFR. Blue galaxies with high SFR or low sSFR are as clustered on large scales as red galaxies. We find that the clustering trend observed with SFR can be explained mostly, but not entirely, by the correlation between stellar mass and clustering amplitude for blue galaxies. We also show that galaxies above the star-forming 'main sequence' are less clustered than galaxies below the main sequence, at a given stellar mass. These results are not consistent with the high-sSFRmore » population being dominated by major mergers. We also measure the clustering amplitude on small scales ({<=}0.3 h {sup -1} Mpc) and find an enhanced clustering signal relative to the best-fit large-scale power law for red galaxies with high stellar mass, blue galaxies with high SFR, and both red and blue galaxies with high sSFR. The increased small-scale clustering for galaxies with high sSFRs is likely linked to triggered star formation in interacting galaxies. These measurements provide strong constraints on galaxy evolution and halo occupation distribution models at z {approx} 1.« less
Neocitreamicins I and II, Novel Antibiotics with Activity against Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci

Two novel antibiotics, neocitreamicins I and II, were isolated from a fermentation broth of a Nocardia strain. This producing strain was obtained using an in situ diffusion chamber that facilitates the cultivation of soil microorganisms. The structures of neocitreamicins I and II were elucidated using UV, MS, and NMR data, and found to be related to the polycyclic xanthone antibiotics of the citreamicin class. The neocitreamicins showed in vitro activity against Gram-positive bacteria including strains of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis.
ON THE ROLE OF THE TROPICS IN THE GENERAL CIRCULATION OF THE ATMOSPHERE

Present knowledge on the role of the tropics in the general circulation is reviewed in comparison with our knowledge twenty years ago. Increasing amounts of upper-air data in the tropics since that time plus the advent of rawin measurements have placed many calculations of the mean seasonal exchange of heat, moisture and angular momentum between the tropics and the extratropical regions on a fairly firm basis. The large troughs seen extending from higher latitudes to the heart of the tropics even with late World War II observations have been confirmed in their role as the principal exchange mechanism. On the other hand, the mean meridional circulation can account for the upward transport of angular momentum which is generated with easterlies within the tropics and also for the net generation of kinetic energy south of 30°N. About 50 per cent of the kinetic energy required north of 30°N in winter to maintain the circulation against frictional dissipation, is imported from the tropics by means of the standing waves of the subtropical jet-stream. Hence it is clear that the tropics help to sustain the kinetic energy of the westerlies and that the tropical circulation is not driven from higher latitudes as often claimed. The sense of total energy transport by the mean meridional circulation inside the tropics is not easily calculated and may even reverse sign. Complications on total energy export also have arisen through the nimbus ii albedo observations which have shown lower albedo (less cloudiness), hence also a larger energy source, for the tropics than previously estimated. It appears certain, merely, that the equatorial trough migrates seasonally so that energy very likely does not pass through it, hence that it constitutes a true “meteorological equator”. No evidence concerning important coupling between the hemispheres across the equator has come to light; however, the new data systems of the next decade may well alter this conclusion. Because of the sensitive computational situation concerning energy transport by the mean meridional circulation, it may be that successful operational application of cloud seeding techniques, such as demonstrated in Project Stormfury in the Caribbean, could exert a subtle influence on the general circulation. This apart, the present status of observational networks is judged to be so far advanced that fluctuations of quantities such as the mean meridional circulation within a season, and in the same month from year to year, can shortly be calculated, possibly shedding light on the variability of the general circulation and precipitation excesses and deficits in tropical regions.
Progress in direct-drive inertial confinement fusion research at the laboratory for laser energetics

Direct-drive inertial confinement fusion (ICF) is expected to demonstrate high gain on the National Ignition Facility (NIF) in the next decade and is a leading candidate for inertial fusion energy production. The demonstration of high areal densities in hydrodynamically scaled cryogenic DT or D2 implosions with neutron yields that are a significant fraction of the “clean” 1-D predictions will validate the ignition-equivalent direct-drive target performance on the OMEGA laser at the Laboratory for Laser Energetics (LLE). This paper highlights the recent experimental and theoretical progress leading toward achieving this validation in the next few years. The NIF will initially be configured for X-ray drive and with no beams placed at the target equator to provide a symmetric irradiation of a direct-drive capsule. LLE is developing the “polar-direct-drive” (PDD) approach that repoints beams toward the target equator. Initial 2-D simulations have shown ignition. A unique “Saturn-like” plastic ring around the equator refracts the laser light incident near the equator toward the target, improving the drive uniformity. LLE is currently constructing the multibeam, 2.6-kJ/beam, petawatt laser system OMEGA EP. Integrated fast-ignition experiments, combining the OMEGA EP and OMEGA Laser Systems, will begin in FY08.
Multilinear generating functions for Charlier polynomials

Charlier configurations provide a combinatorial model for Charlier polynomials. We use this model to give a combinatorial proof of a multilinear generating function for Charlier polynomials. As special cases of the multilinear generating function, we obtain the bilinear generating function for Charlier polynomials and formulas for derangements.