cssi/SciSciGPT-SciSciNet huggingface dataset:
Solution to the initial value problem for a high-gain FEL via Van Kampen's method

Abstract Using Van Kampen's normal mode expansion, we solve the initial value problem for a high-gain free-electron laser described by the three-dimensional Maxwell–Klimontovich equations. An expression of the radiation spectrum is given for the process of coherent amplification and self-amplified spontaneous emission. It is noted that the input coupling coefficient for either process increases with the initial beam energy spread. The effective start-up noise is identified as the coherent fraction of the spontaneous undulator radiation in one field gain length, and is larger with increasing energy spread and emittance mainly because of the increase in gain length.
A Unified Model of Turnover from Organizations

A model of the turnover process is developed by synthesizing three turnover models: those of Price and Mobley and the model which has developed around the organizational commitment variable. This model is tested via path analysis and is generally supported. An attempt to cross-validate the new model also provided reasonable support Jor it.
A Quadratic Lower Bound for Three-Query Linear Locally Decodable Codes over Any Field

A linear (q, δ, ϵ,m(n))-locally decodable code (LDC) C : $ {\mathbb F} $ n → $ {\mathbb F} $ m(n) is a linear transformation from the vector space $ {\mathbb F} $ n to the space $ {\mathbb F} $ m(n) for which each message symbol x i can be recovered with probability at least $ \frac{1}{{\left| \mathbb{F} \right|}} + \varepsilon $ from C(x) by a randomized algorithm that queries only q positions of C(x), even if up to δm(n) positions of C(x) are corrupted. In a recent work of Dvir, the author shows that lower bounds for linear LDCs can imply lower bounds for arithmetic circuits. He suggests that proving lower bounds for LDCs over the complex or real field is a good starting point for approaching one of his conjectures. Our main result is an m(n) = Ω(n 2) lower bound for linear 3-query LDCs over any, possibly infinite, field. The constant in the Ω(·) depends only on e and δ. This is the first lower bound better than the trivial m(n) = Ω(n) for arbitrary fields and more than two queries.
Track formation with bearing and frequency measurements in clutter

Target motion analysis from a narrowband passive sonar that yields bearing and frequency measurements in the presence of false detections (clutter) in a low-SNR (low signal-to-noise ratio) environment is discussed. The likelihood function used to compute the maximum likelihood estimation of the track parameters (localization and frequency) incorporates the false alarms via the probabilistic data association technique. The Cramer-Rao lower bound is calculated and results obtained from simulations are shown to be compatible with it. A test of track acceptance is also presented. >
Failure Detection of Aircraft Engine Output Sensors via Bayesian Hypothesis Testing

Introduction T last two decades have been significant for advancements in control systems. The development of state space analyses has made possible the application of modern control techniques to real problems. The potential for applied modern control theory in the design of future generations of aircraft engines has been recognized by contemporary researchers.' The use of multiple hypothesis testing techniques for detecting the failure state of rate sensors on modern aircraft has been noted. Extension of these ideas to the aircraft engine problem was first considered by De Silva. Further extensions to the problem of large variations in the system output are treated in the present paper.
Delay insertion method in clock skew scheduling

This paper describes a delay insertion method that improves the efficiency of clock skew scheduling. It is shown that reconvergent paths limit the improvement of circuit performance achievable through clock skew scheduling. A delay insertion method is proposed such that the optimal clock period achievable through clock skew scheduling is improved by mitigating the limitations caused by reconvergent paths. Experimental results demonstrate that reconvergent paths are limiting for 34% (41% for level sensitive) of the selected suite of ISCAS'89 benchmark circuits. Through the application of clock skew scheduling with delay insertion, an average improvement of 10% shorter clock periods (9% for level sensitive) is observed for ISCAS'89 benchmark circuits compared to the results of conventional clock skew scheduling.
Threshold corrections to the bottom quark mass revisited

Threshold corrections to the bottom quark mass are often estimated under the approximation that tan β enhanced contributions are the most dominant. In this work we revisit this common approximation made to the estimation of the supersymmetric thresh-old corrections to the bottom quark mass. We calculate the full one-loop supersymmetric corrections to the bottom quark mass and survey a large part of the phenomenological MSSM parameter space to study the validity of considering only the tan β enhanced corrections. Our analysis demonstrates that this approximation underestimates the size of the threshold corrections by ∼ 12.5% for most of the considered parameter space. We discuss the consequences for fitting the bottom quark mass and for the effective couplings to Higgses. We find that it is important to consider the additional contributions when fitting the bottom quark mass but the modifications to the effective Higgs couplings are typically $$ \mathcal{O} $$ (few)% for the majority of the parameter space considered.
The Paradox of Diversification

The current market malaise may keep some investors on the sidelines. The benefits of diversification may not seem as appealing in situations where the constituent investments are likely to lose money. Yet, using relatively simple math, the author shows that diversification maintained by rebalancing can easily turn individual assets’ negative cumulative returns into positive portfolio cumulative returns. This seemingly paradoxical result is the investing analog of a well-known phenomenon studied by physicists and mathematicians called Parrondo’s Paradox.
Noncommutative perturbative dynamics

We study the perturbative dynamics of noncommutative field theories on R d , and find an intriguing mixing of the UV and the IR. High energies of virtual particles in loops produce non-analyticity at low momentum. Consequently, the low energy effective action is singular at zero momentum even when the original noncommutative field theory is massive. Some of the nonplanar diagrams of these theories are divergent, but we interpret these divergences as IR divergences and deal with them accordingly. We explain how this UV/IR mixing arises from the underlying noncommutativity. This phenomenon is reminiscent of the channel duality of the double twist diagram in open string theory.
An Analysis of State-Relevance Weights and Sampling Distributions on L1-Regularized Approximate Linear Programming Approximation Accuracy

Recent interest in the use of L1 regularization in the use of value function approximation includes Petrik et al.'s introduction of L1-Regularized Approximate Linear Programming (RALP). RALP is unique among L1-regularized approaches in that it approximates the optimal value function using off-policy samples. Additionally, it produces policies which outperform those of previous methods, such as LSPI. RALP's value function approximation quality is affected heavily by the choice of state-relevance weights in the objective function of the linear program, and by the distribution from which samples are drawn; however, there has been no discussion of these considerations in the previous literature. In this paper, we discuss and explain the effects of choices in the state-relevance weights and sampling distribution on approximation quality, using both theoretical and experimental illustrations. The results provide insight not only onto these effects, but also provide intuition into the types of MDPs which are especially well suited for approximation with RALP.
Jamming Games in Fast-Fading Wireless Channels

In this paper, we adopt outage probability (lambda-capacity) in fast fading channels as a pay-off function in a zero- sum game between a legitimate transceiver pair and an uncorrelated Gaussian jammer. The transmitter aims at minimizing the outage probability, while the jammer attempts to maximize the outage probability. We consider both peak (over each codeword) and average (over all codewords) power constraints. For peak power constraints, a transmission rate is either supported by the system, or if too large, causes the whole transmission to fail. By imposing average power constraints, large rates can be supported at the cost of positive probability of codeword error. Maxmin and minimax power control strategies are developed, which show that no Nash equilibrium of pure strategies exists under average power constraints.
Give them what they want: The benefits of explicitness in gift exchange

article i nfo Five studies show that gift recipients are more appreciative of gifts they explicitly request than those they do not. In contrast, gift givers assume that both solicited and unsolicited gifts will be equally appreciated. At the root of this dilemma is a difference of opinion about what purchasing an unsolicited gift signals: gift givers expect unsolicited gifts will be considered more thoughtful and considerate by their intended recipients than is actually the case (Studies 1-3). In our final two studies, we highlight two boundary conditions for this effect: identifying a specific gift and using money as a gift. When gift recipients request one specific gift, rather than providing a list of possible gifts, givers become more willing to purchase the requested gift (Study 4). Further, although givers believe that recipients do not appreciate receiving money as much as receiving a solicited gift, recipients feel the opposite about these two gift options (Study 5).
THE IMPACT OF BARYON PHYSICS ON THE STRUCTURE OF HIGH-REDSHIFT GALAXIES

We study the detailed structure of galaxies at redshifts z {>=} 2 using cosmological simulations with improved modeling of the interstellar medium and star formation. The simulations follow the formation and dissociation of molecular hydrogen and include star formation only in cold molecular gas. The molecular gas is more concentrated toward the center of galaxies than the atomic gas, and as a consequence, the resulting stellar distribution is very compact. For halos with total mass above 10{sup 11} M{sub Sun }, the median half-mass radius of the stellar disks is 0.8 kpc at z Almost-Equal-To 3. The vertical structure of the molecular disk is much thinner than that of the atomic neutral gas. Relative to the non-radiative run, the inner regions of the dark matter halo change shape from prolate to mildly oblate and align with the stellar disk. However, we do not find evidence for a significant fast-rotating 'dark disk' of dark matter around the stellar disk. The outer halo regions retain the orientation acquired during accretion and mergers and are significantly misaligned with the inner regions. The radial profile of the dark matter halo contracts in response to baryon dissipation, establishing an approximately isothermal profile throughout most ofmore » the halo. This effect can be accurately described by a modified model of halo contraction. The angular momentum of a fixed amount of inner dark matter is approximately conserved over time, while in the dissipationless case most of it is transferred outward during mergers. The conservation of the dark matter angular momentum provides supporting evidence for the validity of the halo contraction model in a hierarchical galaxy formation process.« less
Copper-Catalyzed Electrophilic Amination of Heteroarenes and Arenes by C–H Zincation

Heteroaromatic amines are key structural motifs that are widely found in biologically important molecules and medicines; therefore, efficient methods for the synthesis of these important heteroaryl amines are highly valuable. Direct amination of heteroarenes and arenes has been achieved in a one-pot C–H zincation/copper-catalyzed electrophilic amination procedure. This amination method provides an efficient and rapid approach to access a diverse range of heteroaromatic and aromatic amines including those previously inaccessible using C–H amination methods. The mild reaction conditions and good functional-group compatibility demonstrate its great potential for the synthesis of important and complex amines.
Auxin and Tryptophan Homeostasis Are Facilitated by the ISS1/VAS1 Aromatic Aminotransferase in Arabidopsis

Indole-3-acetic acid (IAA) plays a critical role in regulating numerous aspects of plant growth and development. While there is much genetic support for tryptophan-dependent (Trp-D) IAA synthesis pathways, there is little genetic evidence for tryptophan-independent (Trp-I) IAA synthesis pathways. Using Arabidopsis , we identified two mutant alleles of ISS1 ( I ndole S evere S ensitive ) that display indole-dependent IAA overproduction phenotypes including leaf epinasty and adventitious rooting. Stable isotope labeling showed that iss1 , but not WT, uses primarily Trp-I IAA synthesis when grown on indole-supplemented medium. In contrast, both iss1 and WT use primarily Trp-D IAA synthesis when grown on unsupplemented medium. iss1 seedlings produce 8-fold higher levels of IAA when grown on indole and surprisingly have a 174-fold increase in Trp. These findings indicate that the iss1 mutant’s increase in Trp-I IAA synthesis is due to a loss of Trp catabolism. ISS1 was identified as At1g80360, a predicted aromatic aminotransferase, and in vitro and in vivo analysis confirmed this activity. At1g80360 was previously shown to primarily carry out the conversion of indole-3-pyruvic acid to Trp as an IAA homeostatic mechanism in young seedlings. Our results suggest that in addition to this activity, in more mature plants ISS1 has a role in Trp catabolism and possibly in the metabolism of other aromatic amino acids. We postulate that this loss of Trp catabolism impacts the use of Trp-D and/or Trp-I IAA synthesis pathways.
Formal and precise derivation of the Green functions for a simple potential

Abstract In formal scattering theory, the Green functions are obtained as solutions of a distributional equation. In this paper, we use the Sturm–Liouville theory to compute the Green functions within a rigorous mathematical theory. We shall show that both the Sturm–Liouville theory and the formal treatment yield the same Green functions. We shall also show how the analyticity of the Green functions as functions of the energy keeps track of the so-called “incoming” and “outgoing” boundary conditions.
From Information Retrieval to Information Interaction

This paper argues that a new paradigm for information retrieval has evolved that incorporates human attention and mental effort and takes advantage of new types of information objects and relationships that have emerged in the WWW environment. One aspect of this new model is attention to highly interactive user interfaces that engage people directly and actively in information seeking. Two examples of these kinds of interfaces are described.
Research accomplishments at the University of Arizona SEMATECH Center of Excellence for contamination/defect assessment and control

The Arizona SEMATECH Center of Excellence (SCOE) was established in May of 1988, is funded by SEMATECH and contractually monitored by the Semiconductor Research Corporation (SRC). The SCOE is engaged in research in a broad front to understand and control contamination which causes yield limiting defects in submicron ULSI circuits. Sandia National Laboratory personnel are integrated with UA personnel in the SCOE research. The focus of the research is on contaminants, both particulates and homogeneous or distributed, which originate in, are caused by, or are transported and deposited by process gases and chemicals or process equipment. Further, the work involves investigating the mapping from contaminants and contaminant levels to degradation of device properties. The resulting degradation in device properties can then be used to estimate the effects of such contaminants for submicron processes and circuits. Results achieved during the four years of the SCOE's existence are described in this paper. >
Simultaneous prediction of RNA secondary structure and helix coaxial stacking

RNA secondary structure plays a scaffolding role for RNA tertiary conformation. Accurate secondary structure prediction can not only identify double-stranded helices and single stranded-loops but also help provide information for potential tertiary interaction motifs critical to the 3D conformation. The average accuracy in ab initio prediction remains 70%; performance improvement has only been limited to short RNA sequences. The prediction of tertiary interaction motifs is difficult without multiple, related sequences that are usually not available. This paper presents research that aims to improve the secondary structure prediction performance and to develop a capability to predict coaxial stacking between helices. Coaxial stacking positions two helices on the same axis, a tertiary motif present in almost all junctions that account for a high percentage of RNA tertiary structures. This research identified energetic rules for coaxial stacks and geometric constraints on stack combinations, which were applied to developing an efficient dynamic programming application for simultaneous prediction of secondary structure and coaxial stacking. Results on a number of non-coding RNA data sets, of short and moderately long lengths, show a performance improvement (specially on tRNAs) for secondary structure prediction when compared with existing methods. The program also demonstrates a capability for prediction of coaxial stacking. The significant leap of performance on tRNAs demonstrated in this work suggests that a breakthrough to a higher performance in RNA secondary structure prediction may lie in understanding contributions from tertiary motifs critical to the structure, as such information can be used to constrain geometrically as well as energetically the space of RNA secondary structure.
Improved Performance of Recursive Tracking Filters Using Batch Initialization and Process Noise Adaptation

Performance of nonlinear recursive tracking filters may be improved using batch initialization and process noise adaptation. These techniques are applied to the problem of radar tracking of a non- maneuvering target vehicle in exoatmospheric flight. Although this problem has received considerable attention in the estimation literature, the approach discussed in this article is new in two respects. The novel features include the method of covariance initialization of the recursive filter and an adaptive model for a process-noise matrix. A batch initialization algorithm generates a covariance matrix with non-zero correlations of position and velocity errors, and this feature accelerates the convergence of errors in the estimates of velocity. The process-noise matrix is based on the gravity-gradient effect, and the tuning method is adaptive because it uses the most recent state estimate and covariance matrix. This feature compensates for nonlinearities in the filter dynamics model, and it improves the agreement between filter covariance and actual errors in the estimates.
Repeated Games with Frequent Signals

We study repeated games with frequent actions and frequent imperfect public signals, where the signals are the aggregate of many discrete events, such as sales or tasks. The high-frequency limit of the equilibrium set depends on both the probability law governing the discrete events and on how many events are aggregated into a single signal. When the underlying events have a binomial distribution, the limit equilibria correspond to the equilibria of the associated continuous-time game with diffusion signals, but other event processes that aggregate to a diffusion limit can have a different set of limit equilibria. Thus the continuous-time game need not be a good approximation of the high-frequency limit whenever the underlying events have three or more possible values.
Differential near-field scanning optical microscopy

A new aperture-type near-field scanning optical microscopy (NSOM) technique, termed differential NSOM (DNSOM) is illustrated. DNSOM utilizes sharp corners of an aperture to beat diffraction-limit, and unlike conventional NSOM, the size of the aperture does not determine the resolution.
Anonymity and information hiding in multiagent systems

We Provide a framework for reasoning about information-hiding requirements in multiagent systems and for reasoning about anonymity in particular. Our framework employs the modal logic of knowledge within the context of the runs and systems framework, much in the spirit of our carlier work on secercy [13]. we give several definitions of anonymity with respect to agents, actions and observers in multiagent systems, and we relate our defenitions of anonymity to other definitions of information hiding, such as secrecy. We also give probabilistic definitions of anonymity that are able to quantify an observer's uncertainty about the state of the system. Finally, we relate our definitions of anonymity to other formalizations of anonymity and information hiding, including defenitions of anonymity in the process algebra CSP and defenitions of information hiding using function views.
Modeling the wall pressure spectrum in turbulent pipe flows

An important source of vibration and noise in piping systems is the fluctuating wall pressure produced by the turbulent boundary layer. One approach to calculating the wall pressure fluctuations is to use a stochastic model based on the Poisson pressure equation. If the model is developed in the wave-number domain, the solution to the wave-number-frequency spectrum can be expressed as an integral of the turbulent sources over the boundary layer thickness. Models based on this formulation have been reported in the literature which show good agreement with measured pressure spectra, but they have relied on adjustable "tuning " constants to account for the unknown properties of the turbulent velocity fluctuations. A variation on this approach is presented in this paper, in which only well-known "universal" constants are used to model the turbulent velocity spectrum. The resulting pressure, spectrum predictions are shown to be in good agreement with canonical data sets over a wide range of Reynolds numbers.
Tuning RED for Web traffic

We study the effects of RED on the performance of Web browsing with a novel aspect of our work being the use of a user-centric measure of performance: response time for HTTP request-response pairs. We empirically evaluate RED across a range of parameter settings and offered loads. Our results show that: (1) contrary to expectations, compared to an FIFO queue, RED has a minimal effect on HTTP response times for offered loads up to 90% of link capacity; (2) response times at loads in this range are not substantially affected by RED parameters; (3) between 90% and 100% load, RED can be carefully tuned to yield performance somewhat superior to FIFO, however, response times are quite sensitive to the actual RED parameter values selected; and (4) in such heavily congested networks, RED parameters that provide the best link utilization produce poorer response times. We conclude that for links carrying only Web traffic, RED queue management appears to provide no clear advantage over tail-drop FIFO for end-user response times.
New directions for the Morita-Baylis-Hillman reaction; homologous aldol adducts via epoxide opening.

Under trialkylphosphine catalyzed Morita–Baylis–Hillman reaction conditions, epoxides react with enones to give rise to homologous aldol adducts.
In-state tuition for undocumented immigrants and its impact on college enrollment, tuition costs, student financial aid, and indebtedness

The 1996 Immigration Reform and Responsibility Act barred states from giving unlawful residents postsecondary education benefits that states do not offer to U.S. citizens. In contrast to this federal law, several states have passed legislation explicitly allowing undocumented immigrants to pay in-state tuition rates. We use a difference-in-difference estimation methodology to assess intended and unintended consequences of this tuition policy. First, we find evidence consistent with past studies that postsecondary enrollment rates of Hispanic non-citizens have increased in treatment states relative to control states without negatively impacting the enrollment rates of native-born Americans. Second, state policies benefiting undocumented immigrants have not increased tuition and fees at comprehensive and community colleges attended by the vast majority of students, though rates have risen at flagship universities. Finally, despite some weak association with increased indebtedness among Hispanic natives, resident tuition subsidies for undocumented immigrants do not appear to have reduced financial aid or increased indebtedness for other demographic groups.
CLOUDS IN THE COLDEST BROWN DWARFS: FIRE SPECTROSCOPY OF ROSS 458C

Condensate clouds are a salient feature of L dwarf atmospheres, but have been assumed to play little role in shaping the spectra of the coldest T-type brown dwarfs. Here we report evidence of condensate opacity in the near-infrared spectrum of the brown dwarf candidate Ross 458C, obtained with the Folded-Port Infrared Echellette (FIRE) spectrograph at the Magellan Telescopes. These data verify the low-temperature nature of this source, indicating a T8 spectral classification, log10 L bol/L ? = ?5.62 ? 0.03, T eff = 650 ? 25 K, and a mass at or below the deuterium burning limit. The data also reveal enhanced emission at the K band associated with youth (low surface gravity) and supersolar metallicity, reflecting the properties of the Ross 458 system (age = 150-800?Myr, [Fe/H] = +0.2 to +0.3). We present fits of FIRE data for Ross 458C, the T9 dwarf ULAS J133553.45+113005.2, and the blue T7.5 dwarf SDSS J141624.08+134826.7B, to cloudless and cloudy spectral models from Saumon & Marley. For Ross 458C, we confirm a low surface gravity and supersolar metallicity, while the temperature differs depending on the presence (635+25 ?35 K) or absence (760+70 ?45 K) of cloud extinction. ULAS J1335+1130 and SDSS J1416+1348B have similar temperatures (595+25 ?45 K), but distinct surface gravities (log g = 4.0-4.5 cgs versus 5.0-5.5 cgs) and metallicities ([M/H] +0.2 versus ?0.2). In all three cases, cloudy models provide better fits to the spectral data, significantly so for Ross 458C. These results indicate that clouds are an important opacity source in the spectra of young cold T?dwarfs and should be considered when characterizing planetary-mass objects in young clusters and directly imaged exoplanets. The characteristics of Ross 458C suggest that it could itself be regarded as a planet, albeit one whose cosmogony does not conform with current planet formation theories.
Is Labor's Loss Capital's Gain? Gross versus Net Labor Shares

US labor share has been falling since the 1970s. I show that it has not fallen as much once items that do not add to capital, depreciation and production taxes, are netted out. Recent net labor share is within its historical range, whereas gross share is at its lowest level. This effect holds for other high-income economies. The overall picture is no longer one of unprecedented, globally declining labor share. Using gross share as a proxy for net share can give misleading results. US gross share and inequality are correlated, whereas net share, the correct measure, is not.
The complex Busemann-Petty problem for arbitrary measures

The complex Busemann-Petty problem asks whether origin symmetric convex bodies in \({\mathbb{C}}^n\) with smaller central hyperplane sections necessarily have smaller volume. The answer is affirmative if \(n \leq 3\) and negative if \(n \geq 4\). In this article we show that the answer remains the same if the volume is replaced by an “almost” arbitrary measure. This result is the complex analogue of Zvavitch’s generalization to arbitrary measures of the original real Busemann-Petty problem.
Duty Cycle Control for Low-Power-Listening MAC Protocols

Energy efficiency is of the utmost importance in wireless sensor networks. The family of Low-Power-Listening MAC protocols was proposed to reduce one form of energy dissipation-idle listening, a radio state for which the energy consumption cannot be neglected. Low-Power-Listening MAC protocols are characterized by a duty cycle: a node probes the channel every t_i {\rm s} of sleep. A low duty cycle favors receiving nodes because they may sleep for longer periods of time, but at the same time, contention may increase locally, thereby reducing the number of packets that can be sent. We propose two new approaches to control the duty cycle so that the target rate of transmitted packets is reached, while the consumed energy is minimized. The first approach, called asymmetric additive duty cycle control (AADCC), employs a linear increase/linear decrease in the t_i value based on the number of successfully received packets. This approach is easy to implement, but it cannot provide an ideal solution. The second approach, called dynamic duty cycle control (DDCC) utilizes control theory to strike a near-optimal balance between energy consumption and packet delivery successes. We generalize both approaches to multihop networks. Results show that both approaches can appropriately adjust t_i to the current network conditions, although the dynamic controller (DDCC) yields results closer to the ideal solution. Thus, the network can use an energy saving low duty cycle, while delivering up to four times more packets in a timely manner when the offered load increases.
Quenching Phase Separation by Vapor Deposition Polymerization

The formation of porous polymer by a template-free, vapor deposition method is studied. Liquid–liquid phase separation of deposited species is quenched by the formation of chemical cross-links. The resulting morphology depends on the relative rates of polymerization, cross-linking, and phase separation. The use of a highly immiscible, liquid porogen results in open-cell, macroporous structures. If an immiscible and crystallizable porogen is employed, porous materials grow as scaffolds of interconnected sheets. The relationship between process conditions and resulting pore-shape and size is evaluated. The ability to control porous polymer growth, morphology, and density can be used in applications to tune modulus and damping characteristics, biological function, or drug delivery at small scales.
Composition and growth effects of the current account: A synthesized portfolio view☆

Abstract This paper analyzes a useful accounting framework that breaks down the current account to two components: a composition effect and a growth effect. We show that past empirical evidence, which strongly supports the growth effect as the main driver of current account dynamics, is misconceived. The remarkable empirical success of the growth effect is driven by the dominance of the cross-sectional variation, which, under conditions met by the data, is generated by an accounting approximation. In contrast to previous findings that the portfolio share of net foreign assets to total assets is constant in a country, both our theoretical and empirical results support a highly persistent process or a unit-root process, with some countries displaying a trend. Finally, we reestablish the composition effect as the quantitatively dominant driving force of current account dynamics in the past data.
Measurement system for low force and small displacement contacts

To support the continued miniaturization of electrical contacts in multichip systems, three-dimensional (3-D) systems, wafer probe cards, and MEMS relays, there is a need for combined measurements of electrical and mechanical phenomena during contact formation. We have carried out a study of electrical contacts in the nN-mN force range for future generation probe cards and novel electronic packaging. One critical phenomenon in the contact formation process is nm-scale deformation of the material layers. To directly study this contact displacement, we have designed a measurement system comprised of a piezoresistive cantilever and an optical interferometer. Together, this system simultaneously measures contact resistance (mOhm to kOhm), force (nN to mN), and displacement (nm-/spl mu/m). These measurements allow the first direct observation of contact mechanical behavior in this important application range. These measurements show that asperities at the contact surface dominate the behavior of the contacts, causing deviations from the Hertzian model of elastic contacts. This paper describes the design and construction of this apparatus, and the operation in a contact mechanics experiment.
Efficacy of intramuscular penicillin in the eradication of group B streptococcal colonization at delivery

Objective. Due to rapid deliveries and human error, not all group B streptococcal positive mothers will receive adequate prophylactic antibiotic treatment in labor. We sought to determine if long acting intramuscular penicillin given after a positive culture result would be efficacious in eradicating group B streptococcal colonization at the time of delivery.Methods. Patients positive for group B streptococci at 35–37 weeks were randomized to receive 2.4 million units of intramuscular benzathine penicillin G suspension (Bicillin® L-A) versus no treatment. Study patients were recultured at the time of admission to labor and delivery prior to receiving prophylactic antibiotics according to CDC guidelines.Results. A total of 53 patients were enrolled. A small but significant decrease in the rate of group B streptococcal colonization was observed in the treatment group (14/27, 52%) versus the control group (20/23, 87%), p = 0.03.Conclusion. The large number of persistent carriers suggests that 2.4 million uni...
Stock prices and top management changes

Abstract This paper studies the association between a firm's stock returns and subsequent top management changes. Consistent with internal monitoring of management, there is an inverse relation between the probability of a management change and a firm's share performance. This relation can result from monitoring by the board, other top managers, or blockholders. However, unless share performance is extremely good or bad, logit models have no predictive ability. No average stock price reaction is detected at announcement of a top management change.
An Independent-Flow-Field Model for a SDOF Nonlinear Structural System–Part II: Analysis of Complex Responses

Complex responses observed in an experimental, nonlinear, moored structural system subjected to nearly periodic wave excitations are examined and compared to the simulations of a newly proposed independent-flow-field (IFF) model in this paper. Variations in wave heights are approximated by additive random perturbations to the dominant periodic component. Simulations show good agreement with the experimental results in both time and frequency domains. Noise effects on the experimental results, including bridging and transition phenomena, are investigated and interpreted by comparing to the simulations of its deterministic counterpart. Possible causes of a chaoticlike experimental result as previously observed are also inferred.
Incorporating the effects of humidity in a mechanistic model of Anopheles gambiae mosquito population dynamics in the Sahel region of Africa

Low levels of relative humidity are known to decrease the lifespan of mosquitoes. However, most current models of malaria transmission do not account for the effects of relative humidity on mosquito survival. In the Sahel, where relative humidity drops to levels <20% for several months of the year, we expect relative humidity to play a significant role in shaping the seasonal profile of mosquito populations. Here, we present a new formulation for Anopheles gambiae sensu lato (s.l.) mosquito survival as a function of temperature and relative humidity and investigate the effect of humidity on simulated mosquito populations. Using existing observations on relationships between temperature, relative humidity and mosquito longevity, we developed a new equation for mosquito survival as a function of temperature and relative humidity. We collected simultaneous field observations on temperature, wind, relative humidity, and anopheline mosquito populations for two villages from the Sahel region of Africa, which are presented in this paper. We apply this equation to the environmental data and conduct numerical simulations of mosquito populations using the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS). Relative humidity drops to levels that are uncomfortable for mosquitoes at the end of the rainy season. In one village, Banizoumbou, water pools dried up and interrupted mosquito breeding shortly after the end of the rainy season. In this case, relative humidity had little effect on the mosquito population. However, in the other village, Zindarou, the relatively shallow water table led to water pools that persisted several months beyond the end of the rainy season. In this case, the decrease in mosquito survival due to relative humidity improved the model’s ability to reproduce the seasonal pattern of observed mosquito abundance. We proposed a new equation to describe Anopheles gambiae s.l. mosquito survival as a function of temperature and relative humidity. We demonstrated that relative humidity can play a significant role in mosquito population and malaria transmission dynamics. Future modeling work should account for these effects of relative humidity.
Gold(I)-catalyzed stereoselective olefin cyclopropanation.

A triphenylphosphinegold(I)-catalyzed cyclopropanation of olefins using propargyl esters as gold(I)−carbene precursors is reported. This reaction provided the basis for the use of a DTBM-SEGPHOS gold(I) complex as a catalyst in the enantioselective (up to 94% ee) preparation of vinyl cyclopropanes with high cis-selectivity.
A new Tevatron Collider working point near the integer

It is well established that in hadron colliders the beam-beam interaction is more harmful in the presence of machine resonances of the form mv/sub x/+nv/sub y/=p, where mod m mod + mod n mod is the order of the resonance. Since the closest a resonance line can be to the integer stopband is 1/order, the closer the working point is to the integer, the fewer lower-order resonances there are to enhance the beam-beam effects. A shift of the working point of the Tevatron from 19.4 to values near 19 and 20 has been studied. Problems with closed-orbit control, dispersion matching, and matched low beta insertions were considered. An excellent solution for the B0 insertion was found which has an improved beta *. A new injection optics allows a transition to the low beta optics which is much easier than the one now used. Results from the first machine studies demonstrate the ability to control the orbit with tunes of 19.03 horizontal and 20.03 vertical. Further studies require the activation of additional quadrupole compensation circuits. >
Surgical Approaches to Orbital Tumors

Three approaches as used with modern technology, magnification with an operating microscope, and self-retained retraction have been presented. These approaches have allowed satisfactory exposure of difficult retrobulbar orbital areas from the various directions and have allowed us to more comfortably microdissect and remove orbital tumors. They also provide good exposure for the use of the carbon dioxide laser, which has been an aid in removing the intraorbital extensions of meningiomas, plexiform neurofibromas, and difficult lymphangiomas that occupy the intraconal compartments of the orbit. These approaches should only be undertaken by a skilled ophthalmic orbital surgical team in the case of the anterior medial and lateral approach, and definitely by a well-experienced neurosurgical/ophthalmic orbital team for tumors involving the orbital cranial junction and the superior orbital compartment. Experience gained over 17 years has convinced us that a team approach is mandatory for the difficult deep intraorbital tumors, even with the anterior medial or lateral approach.
The planting real option in cash rent valuation

After entering into a farmland cash rent contract in the fall, a tenant farmer has flexibility over the spring crop choice and the input application level. Failure to account for these options will bias estimates of what farmers should pay to rent land. Applying Monte Carlo simulation methods, this study investigates the option values for these choices. A Multivariate Gaussian Copula (MGC) is employed to account for dependence among yields and prices. Results show that the average cash rent valuation for the real option approach is $33.6 higher than that for the conventional Net Present Value (NPV) method, in which the input intensity option is $0.9. Crop planting sequence is shown to impact the real option value.
Invariant tests for spatial stationarity using covariance structure

We propose new tests for validating the ULA model based on the received array data. These tests use the structure of the covariance matrix of the data to decide whether the received data is spatially stationary. Invariance principles are used to ensure that the test has constant significance (equivalent to a CFAR test) when the model is indeed true by eliminating the dependence on the covariance. In addition, a modification of the test is proposed for verifying stationarity within a specified subspace, and heuristics are presented for distinguishing propagation effects from deviation from the ULA model.
On the Landau-Ginzburg description of N=2 minimal models

The conjecture that N=2 minimal models in two dimensions are critical points of a superrenormalizable Landau-Ginzburg model can be tested by computing the path integral of the Landau-Ginzburg model with certain twisted boundary conditions. This leads to simple expressions for certain characters of the N=2 models which can be verified at least at low levels. An N=2 superconformal algebra can in fact be found directly in the noncritical Landau-Ginzburg system, giving further support for the conjecture.
The Determination of the Probabilistic Properties of Velocities and Accelerations in Kinematic Chains With Uncertainty

A probabilistic model and methods to determine the means and variances of the velocity and acceleration within stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link’s effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data is the nominal linkage model and statistical information. The “effective link length” model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper solves the higher-order kinematics problem for the probabilistic design analysis of stochastically defined mechanisms.
Allergan‐isopropyl alcohol emissions removal using a unique biological system

Allergan constructed and is operating a unique biological system designed to reduce emissions of isopropyl alcohol (IPA) as well as acetone and heptane from intaocular lens manufacturing operations. The exhaust gases from the manufacturing facility are passed through a pair of wet scrubbers, in series, that allow mass transfer of the IPA from air to water. The original design called for packed towers to be used to partially biochemically oxidize the emissions. This design was changed after three months, due to fouling problems, to simply a water stripper mode of operation. Then, the water stream is passed through a fixed film bioreactor to reduce the final concentration of IPA and other emissions to less than 99% of the total inlet concentration. The inlet concentrations treated by the system ranged from 200 to 500 mg/m3 at a flow rate of 5000 cfm. On average, the system treated approximately 12 gallons per day of IPA and lesser amounts of acetone and heptane. The system is a closed system and only requires the addition of bacteria and nutrients on a periodic basis. Sludge is removed periodically. The system was started on May 18, 1997 and went through a startup validation which was completed in December of 1997. The operational data is presented along with the method of startup and methods to overcome adverse operating conditions. The system from two weeks after startup has maintained an IPA removal efficiency of greater than 99%. Nutrient loading and pH adjustment have been fine tuned during the startup validation period. The system has proved to be as economical as first described in a previous paper as compared to other control devices such as catalytic thermal oxidation.
Stille reactions catalytic in tin: a "Sn-F" route for intermolecular and intramolecular couplings.

Polymethylhydrosiloxane (PMHS) made hypercoordinate by KF(aq) allows Me3SnH to be recycled during a Pd(0)-catalyzed hydrostannation/Stille cascade. Starting with a variety of alkynes, in situ vinyltin formation is followed by Stille reaction with aryl, styryl, benzyl, or vinyl electrophiles present in the reaction mixture. Both inter- and intramolecular versions of the process are possible with tin loads of approximately 6 mol %. Regeneration of the organotin hydride is believed to proceed through a Me3SnF intermediate. Given the aggregated nature of organotin fluorides and the ability to use these organotins in substoichiometric quantities, the hazards and purification problems associated with the removal of organotin wastes from reaction mixtures are minimized.
A New Algorithm for Simultaneous Gate Sizing and Threshold Voltage Assignment

Gate sizing and threshold voltage (Vt) assignment are popular techniques for circuit timing and power optimization. Existing methods, by and large, are either sensitivity-driven heuristics or based on discretizing continuous optimization solutions. Sensitivity-driven heuristics are easily trapped in local optima and the discretization may be subject to remarkable errors. In this paper, we propose a systematic combinatorial approach for simultaneous gate sizing and Vt assignment. The core idea of this approach is joint relaxation and restriction, which employs consistency relaxation and coupled bi-directional solution search. The process of joint relaxation and restriction is conducted iteratively to systematically improve solutions. Our algorithm is compared with a state-of-the-art previous work on benchmark circuits. The results from our algorithm can lead to about 22% less power dissipation subject to the same timing constraints.
Constraints in Databases

Recently, interest in constraints and databases has increased significantly as the databases field has started to consider broader application domains. In this short position statement, I identify some of the most promising direcrtions, in my opinion, for the use of constraints in the context of databaes management systems.