cssi/SciSciGPT-SciSciNet huggingface dataset:
Principal components in linear mixed models with general bulk

We study the principal components of covariance estimators in multivariate mixed-effects linear models. We show that, in high dimensions, the principal eigenvalues and eigenvectors may exhibit bias and aliasing effects that are not present in low-dimensional settings. We derive the first-order limits of the principal eigenvalue locations and eigenvector projections in a high-dimensional asymptotic framework, allowing for general population spectral distributions for the random effects and extending previous results from a more restrictive spiked model. Our analysis uses free probability techniques, and we develop two general tools of independent interest—strong asymptotic freeness of GOE and deterministic matrices and a free deterministic equivalent approximation for bilinear forms of resolvents.
Teacher-Student Neural Coupling During Teaching and Learning.

Human communication is remarkably versatile, enabling teachers to share highly abstracted and novel information with their students. What neural processes enable such transfer of information across brains during naturalistic teaching and learning? Here, a teacher was scanned in fMRI giving an oral lecture with slides on a scientific topic followed by a review lecture. Students were then scanned watching either the intact lecture and review (N = 20) or a temporally scrambled version of the lecture (N = 20). Using intersubject correlation (ISC), we observed widespread teacher-student neural coupling spanning sensory cortex and language regions along the superior temporal sulcus as well as higher-level regions including posterior medial cortex (PMC), superior parietal lobule (SPL), and dorsolateral and dorsomedial prefrontal cortex. Teacher-student alignment in higher-level areas was not observed when learning was disrupted by temporally scrambling the lecture. Moreover, teacher-student coupling in PMC was significantly correlated with learning: the more closely the student's brain mirrored the teacher's brain, the more the student improved their learning score. Together, these results suggest that the alignment of neural responses between teacher and students may reflect effective communication of complex information across brains in classroom settings.
Drosophila re-zero their path integrator at the center of a fictive food patch

Summary The ability to keep track of one’s location in space is a critical behavior for animals navigating to and from a salient location, and its computational basis is now beginning to be unraveled. Here, we tracked flies in a ring-shaped channel as they executed bouts of search triggered by optogenetic activation of sugar receptors. Unlike experiments in open field arenas, which produce highly tortuous search trajectories, our geometrically constrained paradigm enabled us to monitor flies’ decisions to move toward or away from the fictive food. Our results suggest that flies use path integration to remember the location of a food site even after it has disappeared, and flies can remember the location of a former food site even after walking around the arena one or more times. To determine the behavioral algorithms underlying Drosophila search, we developed multiple state transition models and found that flies likely accomplish path integration by combining odometry and compass navigation to keep track of their position relative to the fictive food. Our results indicate that whereas flies re-zero their path integrator at food when only one feeding site is present, they adjust their path integrator to a central location between sites when experiencing food at two or more locations. Together, this work provides a simple experimental paradigm and theoretical framework to advance investigations of the neural basis of path integration.
What Contributes to a Crowdfunding Campaign's Success? Evidence and Analyses from GoFundMe Data

Researchers have attempted to measure the success of crowdfunding campaigns using a variety of determinants, such as the descriptions of the crowdfunding campaigns, the amount of funding goals, and crowdfunding project characteristics. Although many successful determinants have been reported in the literature, it remains unclear whether the cover photo and the text in the title and description could be combined in a fusion classifier to better predict the crowdfunding campaign's success. In this work, we focus on the performance of the crowdfunding campaigns on GoFundMe across a wide variety of funding categories. We analyze the attributes available at the launch of the campaign and identify attributes that are important for each category of the campaigns. Furthermore, we develop a fusion classifier based on the random forest that significantly improves the prediction result, thus suggesting effective ways to make a campaign successful.
Adaptive phenotypic plasticity stabilizes evolution in fluctuating environments

Fluctuating environmental conditions are ubiquitous in natural systems, and populations have evolved various strategies to cope with such fluctuations. The particular mechanisms that evolve profoundly influence subsequent evolutionary dynamics. One such mechanism is phenotypic plasticity, which is the ability of a single genotype to produce alternate phenotypes in an environmentally dependent context. Here, we use digital organisms (self-replicating computer programs) to investigate how adaptive phenotypic plasticity alters evolutionary dynamics and influences evolutionary outcomes in cyclically changing environments. Specifically, we examined the evolutionary histories of both plastic populations and non-plastic populations to ask: (1) Does adaptive plasticity promote or constrain evolutionary change? (2) Are plastic populations better able to evolve and then maintain novel traits? And (3), how does adaptive plasticity affect the potential for maladaptive alleles to accumulate in evolving genomes? We find that populations with adaptive phenotypic plasticity undergo less evolutionary change than non-plastic populations, which must rely on genetic variation from de novo mutations to continuously readapt to environmental fluctuations. Indeed, the non-plastic populations undergo more frequent selective sweeps and accumulate many more genetic changes. We find that the repeated selective sweeps in non-plastic populations drive the loss of beneficial traits and accumulation of maladaptive alleles, whereas phenotypic plasticity can stabilize populations against environmental fluctuations. This stabilization allows plastic populations to more easily retain novel adaptive traits than their non-plastic counterparts. In general, the evolution of adaptive phenotypic plasticity shifted evolutionary dynamics to be more similar to that of populations evolving in a static environment than to non-plastic populations evolving in an identical fluctuating environment. All natural environments subject populations to some form of change; our findings suggest that the stabilizing effect of phenotypic plasticity plays an important role in subsequent adaptive evolution.
Trade-In or Sell in My P2P Marketplace: A Game Theoretic Analysis of Profit and Environmental Impact

With more customers purchasing pre-owned or used products in the apparel industry, firms are increasingly adopting resale based business models generally through either a: (i) trade-in with a resale program, where a firm offers a trade-in discount on a new product and resells the traded-in products, or a (ii) P2P resale marketplace, where the firm facilitates a resale marketplace in which customers can buy and sell used products to each other. Since both resale strategies are utilized by different apparel firms, it is not clear which strategy is more profitable in a given context. Further, firms that adopt each resale model also promote their environmental benefits and there are concerns that these firms are green-washing, i.e., misrepresenting the environmental benefits of their business models. Although it is an important issue for the apparel industry, to the best of our knowledge, the literature has not rigorously analyzed the profitability and environmental impacts of the trade-in and P2P models concurrently. We attempt to fill this gap in the literature and investigate the profitability and environmental impacts of the trade-in and P2P resale marketplace models. We find that the trade-in model may be more profitable despite the lower reverse logistics cost in the P2P model, and P2P resale marketplace may be more profitable despite the trade-in program having direct control over the supply and demand of used products. Furthermore, interestingly, both models can be better for the environment depending on the product's environmental characteristics. However, we also find that when customers are extremely forward-looking, interestingly, the trade-in model always has a lower environmental footprint than the P2P model. Based on our analysis, we further create a matrix of product attributes and identify when each resale business model is better for profitability and environment concurrently, and also when there is misalignment in the same regard. We also study the impact of product durability on pricing for both trade-in and P2P models. In addition, we present several other results and managerial insights that would provide useful guidelines not only for apparel firms, but also for non-governmental organizations and environmental advocacy groups.
Pattern selection in the Schnakenberg equations: From normal to anomalous diffusion

Pattern formation in the classical and fractional Schnakenberg equations is studied to understand the nonlocal effects of anomalous diffusion. Starting with linear stability analysis, we find that if the activator and inhibitor have the same diffusion power, the Turing instability space depends only on the ratio of diffusion coefficients $\kappa_1/\kappa_2$. However, the smaller diffusive powers might introduce larger unstable wave numbers with wider band, implying that the patterns may be more chaotic in the fractional cases. We then apply a weakly nonlinear analysis to predict the parameter regimes for spot, stripe, and mixed patterns in the Turing space. Our numerical simulations confirm the analytical results and demonstrate the differences of normal and anomalous diffusion on pattern formation. We find that in the presence of superdiffusion the patterns exhibit multiscale structures. The smaller the diffusion powers, the larger the unstable wave numbers and the smaller the pattern scales.
Selective Breeding for Disease-Resistant PRNP Variants to Manage Chronic Wasting Disease in Farmed Whitetail Deer.

Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy (TSE) of cervids caused by a misfolded variant of the normal cellular prion protein, and it is closely related to sheep scrapie. Variations in a host’s prion gene, PRNP, and its primary protein structure dramatically affect susceptibility to specific prion disorders, and breeding for PRNP variants that prevent scrapie infection has led to steep declines in the disease in North American and European sheep. While resistant alleles have been identified in cervids, a PRNP variant that completely prevents CWD has not yet been identified. Thus, control of the disease in farmed herds traditionally relies on quarantine and depopulation. In CWD-endemic areas, depopulation of private herds becomes challenging to justify, leading to opportunities to manage the disease in situ. We developed a selective breeding program for farmed white-tailed deer in a high-prevalence CWD-endemic area which focused on reducing frequencies of highly susceptible PRNP variants and introducing animals with less susceptible variants. With the use of newly developed primers, we found that breeding followed predictable Mendelian inheritance, and early data support our project’s utility in reducing CWD prevalence. This project represents a novel approach to CWD management, with future efforts building on these findings.
Tollmien-Schlichting route to elastoinertial turbulence in channel flow

Elastoinertial turbulence (EIT) in dilute polymer solutions displays tilted sheets of polymer stretch with weak spanwise-oriented flow structures -- a sharp contrast to the three-dimensional quasistreamwise vortex structures that make up inertia-driven Newtonian turbulence. We show that at for channel flow at sufficiently high Reynolds number, the Newtonian nonlinear Tollmien-Schlichting (TS) wave evolves continuously into EIT as the Weissenberg number increases, highlighting in particular a ``sheet-shedding'' process by which individual sheets are born in the Kelvin cat's eye structure of the TS wave and break up to form the layered multi-sheet structure characteristic of EIT.
Task-Oriented Low-Dose CT Image Denoising.

The extensive use of medical CT has raised a public concern over the radiation dose to the patient. Reducing the radiation dose leads to increased CT image noise and artifacts, which can adversely affect not only the radiologists judgement but also the performance of downstream medical image analysis tasks. Various low-dose CT denoising methods, especially the recent deep learning based approaches, have produced impressive results. However, the existing denoising methods are all downstream-task-agnostic and neglect the diverse needs of the downstream applications. In this paper, we introduce a novel Task-Oriented Denoising Network (TOD-Net) with a task-oriented loss leveraging knowledge from the downstream tasks. Comprehensive empirical analysis shows that the task-oriented loss complements other task-agnostic losses by steering the denoiser to enhance the image quality in the task related regions of interest. Such enhancement in turn brings general boosts on the performance of various methods for the downstream task. The presented work may shed light on the future development of context-aware image denoising methods. Code is available at https://github.com/DIAL-RPI/Task-Oriented-CT-Denoising_TOD-Net.
A Modular and Transferable Reinforcement Learning Framework for the Fleet Rebalancing Problem

Mobility on demand (MoD) systems show great promise in realizing flexible and efficient urban transportation. However, significant technical challenges arise from operational decision making associated with MoD vehicle dispatch and fleet rebalancing. For this reason, operators tend to employ simplified algorithms that have been demonstrated to work well in a particular setting. To help bridge the gap between novel and existing methods, we propose a modular framework for fleet rebalancing based on model-free reinforcement learning (RL) that can leverage an existing dispatch method to minimize system cost. In particular, by treating dispatch as part of the environment dynamics, a centralized agent can learn to intermittently direct the dispatcher to reposition free vehicles and mitigate against fleet imbalance. We formulate RL state and action spaces as distributions over a grid partitioning of the operating area, making the framework scalable and avoiding the complexities associated with multiagent RL. Numerical experiments, using real-world trip and network data, demonstrate that RL reduces waiting time by 28% to 38% for the same-day evaluation, 17% to 44% for cross-day evaluation, and 22% to 25% for cross-season evaluation compared with no rebalancing scenarios. This approach has several distinct advantages over baseline methods including: improved system cost; high degree of adaptability to the selected dispatch method; and the ability to perform scale-invariant transfer learning between problem instances with similar vehicle and request distributions.
An Unfitted Finite Element Method for Two-Phase Stokes Problems with Slip Between Phases

We present an isoparametric unfitted finite element approach of the CutFEM or Nitsche-XFEM family for the simulation of two-phase Stokes problems with slip between phases. For the unfitted generalized Taylor–Hood finite element pair $${\mathbf {P}}_{k+1}-P_k$$ , $$k\ge 1$$ , we show an inf-sup stability property with a stability constant that is independent of the viscosity ratio, slip coefficient, position of the interface with respect to the background mesh and, of course, mesh size. In addition, we prove stability and optimal error estimates that follow from this inf-sup property. We provide numerical results in two and three dimensions to corroborate the theoretical findings and demonstrate the robustness of our approach with respect to the contrast in viscosity, slip coefficient value, and position of the interface relative to the fixed computational mesh.
Pedestrian Emergence Estimation and Occlusion-Aware Risk Assessment for Urban Autonomous Driving

Avoiding unseen or partially occluded vulnerable road users (VRUs) is a major challenge for fully autonomous driving in urban scenes. However, occlusion-aware risk assessment systems have not been widely studied. Here, we propose a pedestrian emergence estimation and occlusion-aware risk assessment system for urban autonomous driving. First, the proposed system utilizes available contextual information, such as visible cars and pedestrians, to estimate pedestrian emergence probabilities in occluded regions. These probabilities are then used in a risk assessment framework, and incorporated into a longitudinal motion controller. The proposed controller is tested against several baseline controllers that recapitulate some commonly observed driving styles. The simulated test scenarios include randomly placed parked cars and pedestrians, most of whom are occluded from the ego vehicle's view and emerges randomly. The proposed controller outperformed the baselines in terms of safety and comfort measures.
Strategic thinking in contests

We examine motives for ‘overbidding’ in contests between individuals using a “two-headed” approach to decision-making. In “two-headed” contests, subject pairs send suggested bids and messages to a partner. Content analysis of the messages provides insight into an individual’s bidding motives. In addition, we elicit measures of preferences, beliefs, and impulsiveness. We find that beliefs about others’ bids and messages that emphasize winning (i.e., utility of winning) are the most robust predictors of ‘overbidding’. Our results suggest that analyzing communication provides a rich window into an individual’s thought process when making decisions, and can complement insights from elicited values from common decision tasks (Replication materials, including data, do files, and software, are available at https://sites.google.com/view/david-bruner/research ).
Formal Guarantees of Timely Progress for Distributed Knowledge Propagation

Autonomous air traffic management (ATM) operations for urban air mobility (UAM) will necessitate the use of distributed protocols for decentralized coordination between aircraft. As UAM operations are time-critical, it will be imperative to have formal guarantees of progress for the distributed protocols used in ATM. Under asynchronous settings, message transmission and processing delays are unbounded, making it impossible to provide deterministic bounds on the time required to make progress. We present an approach for formally guaranteeing timely progress in a Two-Phase Acknowledge distributed knowledge propagation protocol by probabilistically modeling the delays using theories of the Multicopy Two-Hop Relay protocol and the M/M/1 queue system. The guarantee states a probabilistic upper bound to the time for progress as a function of the probabilities of the total transmission and processing delays being less than two given values. We also showcase the development of a library of formal theories, that is tailored towards reasoning about timely progress in distributed protocols deployed in airborne networks, in the Athena proof assistant.
Robust and differentially private mean estimation

Differential privacy has emerged as a standard requirement in a variety of applications ranging from the U.S. Census to data collected in commercial devices, initiating an extensive line of research in accurately and privately releasing statistics of a database. An increasing number of such databases consist of data from multiple sources, not all of which can be trusted. This leaves existing private analyses vulnerable to attacks by an adversary who injects corrupted data. Despite the significance of designing algorithms that guarantee privacy and robustness (to a fraction of data being corrupted) simultaneously, even the simplest questions remain open. For the canonical problem of estimating the mean from i.i.d. samples, we introduce the first efficient algorithm that achieves both privacy and robustness for a wide range of distributions. This achieves optimal accuracy matching the known lower bounds for robustness, but the sample complexity has a factor of $d^{1/2}$ gap from known lower bounds. We further show that this gap is due to the computational efficiency; we introduce the first family of algorithms that close this gap but takes exponential time. The innovation is in exploiting resilience (a key property in robust estimation) to adaptively bound the sensitivity and improve privacy.
Transfer learning for high‐dimensional linear regression: Prediction, estimation and minimax optimality

This paper considers the estimation and prediction of a high-dimensional linear regression in the setting of transfer learning, using samples from the target model as well as auxiliary samples from different but possibly related regression models. When the set of "informative" auxiliary samples is known, an estimator and a predictor are proposed and their optimality is established. The optimal rates of convergence for prediction and estimation are faster than the corresponding rates without using the auxiliary samples. This implies that knowledge from the informative auxiliary samples can be transferred to improve the learning performance of the target problem. In the case that the set of informative auxiliary samples is unknown, we propose a data-driven procedure for transfer learning, called Trans-Lasso, and reveal its robustness to non-informative auxiliary samples and its efficiency in knowledge transfer. The proposed procedures are demonstrated in numerical studies and are applied to a dataset concerning the associations among gene expressions. It is shown that Trans-Lasso leads to improved performance in gene expression prediction in a target tissue by incorporating the data from multiple different tissues as auxiliary samples.
The Concept of Legitimacy in International Law

The paper that I circulated for today’s meeting built on an article that I wrote in the American Journal of International Law back in 1999. At that time, relatively little had been written about the issue of legitimacy by international lawyers, except for Tom Frank’s pioneering book1 and some more topical papers such as David Caron’s paper analysing the legitimacy of the Security Council.2 In the last decade, there has been an explosion of interest in the problem of international legitimacy — what one writer has called a veritable renaissance in international legitimacy talk.3 This, I think, reflects the growing authority and importance of international institutions. When international institutions were relatively weak, legitimacy was not a pressing issue. But as they have become more influential, and as the need has grown for international institutions with greater authority to address collective problems such as climate change, this has prompted more questions about what will make such institutions legitimate.
A novel MMIC active filter with lumped and transversal elements

An active filter structure is described and demonstrated as a monolithic microwave integrated current (MMIC). The filter structure makes use of both lumped elements and active transversal elements. The combination of lumped and transversal elements provides performance superior to that of a filter made of lumped elements alone and is much smaller than a filter made of transversal elements alone. This miniature MMIC filter has a passband of 9.8-11.1 GHz with 2-dB loss, and better than 30 dB rejection 1.1 GHz from either passband edge. This level of performance could not have been achieved on a conventional 4-mil-thick GaAs MMIC with only passive lumped elements. >
The presence of DNA sequences Related to a 4.2Kb cryptic plasmid in the chromosomes of plasmid-free strains of Neisseria gonorrhoeae

Most strains of Neisseria gonorrhoeae contain a 4.2-Kb cryptic plasmid. However, strains that do not possess the 4.2Kb plasmid have been isolated. We examined 38 such strains and found that five of them contained chromosomal sequences homologous to the 4.2Kb plasmid. Restriction analysis and hybridization of 4.2Kb plasmid DNA to blots of the agarose gels suggested that homology with the 4.2Kb plasmid occurred at a single chromosomal site that was the same for all five strains. Similar experiments showed that these sequences derived from the 2.7Kb Hinfl (HinfIA) fragment of the cryptic plasmid. None of these five strains or two additional strains that exhibited no homology with the plasmid had sequences homologous with the 1.5Kb Hinfl fragment. When the region homologous to the HinfIA fragment was cloned from the chromosomal DNA of one strain, it was found to comprise the entire HinfIA fragment of the plasmid.
Who Counts in the Census? Racial and Ethnic Categories in France

The question of racial and ethnic statistics is part of a debate in France that has been going on for 20 years now: indeed France’s census (performed by the INSEE, Institut National de la Statistique et des etudes economiques or National Institute of Statistics and Economic Studies) does not include racial or ethnic categories. Furthermore, it is illegal for French structures and institutions (schools, universities, employers, corporations and public administrations) to request and hold information that includes racial or ethnic categories. At the same time, over the years, there have been several attempts – mostly unsuccessful- by scholars, non-governmental organizations and also elected officials, to argue in favor of the inclusion of ethnic statistics, as it has come to be called. This chapter will first present a demographic profile and trends of France, and then expose the methodological and theoretical issues related to the seemingly color-blindness of the French census.
Property Rights and the Dynamics of Renewable Resources in North-South Trade

To explain the patterns of world trade of resources, this paper combines the biological dynamics of the renewable resource and game theoretical explanations of its extraction under different property regimes, with a general equilibrium model of North South trade (Chichilnisky, 1981, 1986). The two regions produce, consume and trade two goods using two inputs, a renewable resource E and capital. To expose the importance of property rights in explaining trade, the two regions are taken as identical except for the property rights regimes on the pool from which the resource is extracted: the South has common property and the North private property. The paper formulates the Nash equilibrium of a game which explains the harvesting of the resource under different property rights regimes: more is supplied at each price under unregulated property rights than it is with private property (Lemma 1). Theorem 1 proves that the difference in property rights by itself explains trade between otherwise identical regions: the South exports the environmentally intensive product even though it has no comparative advantage and the North the capital intensive products. The North overconsumes the resource intensive products which it imports at prices which are below social costs. This occurs even though in equilibrium the prices of all goods and all factors of production are equal across the world. Resources are overextracted and the world pattern of consumption and trade of resources is Pareto inefficient. Several policies which could redress the inefficiency, particularly recent property rights policies towards biodiversity and land ownership in the Americas, are discussed in this paper.
Foundations for Bidirectional Programming

Most programs get used in just one direction, from input to output. But sometimes, having computed an output, we need to be able to update this output and then "calculate backwards" to find a correspondingly updated input. The problem of writing such bidirectional transformations ---often called lenses ---arises in applications across a multitude of domains and has been attacked from many perspectives [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16, etc.]. See [17] for a detailed survey.
Characterizing the dayside magnetosheath using energetic neutral atoms: IBEX and THEMIS observations

[1] We report on the time evolution of energetic neutral atom (ENA) emissions measured by the Interstellar Boundary Explorer (IBEX) during instances of compressed and expanded dayside magnetosheath. The ENA observations, taken during the passage of a corotating interaction region on 27 and 28 November 2010, are compared with in situ observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. IBEX's field of view (6.5° full width at half maximum) covered a wide region of the dayside magnetosheath for several days, providing continuous information from that region. The high sensitivity and high-energy resolution of IBEX instruments enabled unprecedented remote-sensing diagnostics of dayside magnetosheath ENA spectra at energies between ~0.1 and ~6 keV, which can be directly compared with various upstream parameters. The inferred plasma spectra from ENA observations showed characteristic suprathermal tails described by kappa distributions that correlate well with the solar wind cone angle and are in agreement with in situ observations, suggesting that the shock angle contributed to magnetosheath particle heating. Simultaneous in situ ion measurements in the dayside magnetosheath provided by THEMIS agree reasonably well with IBEX-inferred spectra, demonstrating synergy between remote IBEX ENA observations (global) and in situ measurements (local) for studying localized magnetospheric processes.
Refinement of the structure of beta-chitin.

The structure of β-chitin has been refined by rigid-body least-squares methods, based on the intensity data for highly crystalline specimens from the pogonophore Oligobrachia ivanovi. The structure consists of an array of poly-N-acetyl-D-glucosamine chains all having the same sense, which are linked together in sheets by NH … OC hydrogen bonding of the amide groups. In addition to the O-3′H … O-5 intramolecular hydrogen bond, analogous to that in cellulose, the CH2OH side chain forms an intrasheet hydrogen bond to the carbonyl oxygen on the next chain. This structure shows considerably better agreement between observed and calculated intensities than that possessing an intersheet hydrogen bond, as had been proposed previously. The structure is consistent with the swelling properties of β-chitin and can also be seen to be analogous to that of native cellulose.
Suprapubic endoscopy for interval female sterilization

Minilaparotomy delivery systems have been developed for rings and clips due to increased popularity and elimination of the hazards of electrocoagulation. The open laparoscopy technique eliminated the use of needle insufflation and blind introduction of a sharp trocar. Endoscopic sterilization combines the advantages of a minilaparotomy incision with intrapelvic tubal occlusion. Suprapubic endoscopic sterilization requires: 1) proper elevation of the uterus so the fundus is near the abdominal wall; 2) use of a trocar sleeve with blunt obtuator; and 3) employment of a Trendelenburg position of 35 degrees or greater. The suprapubic endoscopic approach eliminates the use of sharp trocars and needles intraperitoneal electrical current and the need for intra-abdominal insufflation.
Implications of cost and bid format on electricity market studies: linear versus quadratic costs

One important assumption in a model of an electricity market is the format of bids and costs. Most literature on electricity markets uses piecewise linear or quadratic functions to represent cost and bid. Economic theory holds that a firm in a perfectly competitive market maximizes its profit when it sells at marginal cost. This implies that profit-maximizing generators bid at marginal cost. Different markets have varying rules regarding bid formats. Piecewise linear bid curves are compatible with physical characteristics of electricity generators, but cause difficulties in certain analysis techniques. Quadratic bid curves provide smooth dispatch, revenue, and profit curves that facilitate calculus-based analysis. In profit calculations, bids and marginal costs may either be coupled or independent of each other. The relation between bids and marginal costs impacts the profit-maximizing bid, and thus impacts generator strategies. These assumptions arc particularly important for marginal generators, since different bid structures may yield different dispatch results, especially if the system is constrained. We compare markets with all piecewise linear bids, all quadratic bids, and a mixture of bids, and study the impacts of bid format and profit calculation on market outcomes in different scenarios.
Quantitative approaches for assessing the value of COTS-centric development

Software development based on commercial off-the-shelf or COTS, components is currently drawing considerable attention. This paper presents the results of two complementary quantitative valuation methods applied to the assessment of the COTS-centric software development projects. We use a standard corporate finance tool, Net Present Value, as a basis for both methods. The first method, comparative valuation, investigates the economic incentive to choose the COTS centric strategy in a project vis a vis the alternative, the custom development strategy, through an incentive metric based on NPV. The analysis concentrates on the impact of product risk and development time on the defined metric. The second method, real options valuation, primarily deals with uncertainty. It is employed to investigate the value of strategic flexibility inherent in COTS-centric development. We provide examples of several such options and summarize qualitatively the results of their analyses. Using these two approaches, some common anecdotes of COTS-centric development can be substantiated by sound financial arguments. Through scenarios and sensitivity analyses, we show that different circumstances and assumptions give rise to different winning conditions. Some general principles are summarized at the end.
Comparison of mitomycin C trabeculectomy, glaucoma drainage device implantation, and laser neodymium:YAG cyclophotocoagulation in the management of intractable glaucoma after penetrating keratoplasty.

Abstract Purpose This study aimed to compare the surgical outcomes of mitomycin C trabeculectomy glaucoma drainage device (GDD) surgery and laser neodymium:YAG (Nd:YAG) cyclophotocoagulation (CPC) in the management of intractable glaucoma after penetrating keratoplasty (PKP) in a retrospective study. Design Interventional case series. Participants/methods The medical charts of consecutive patients who had pre-existing glaucoma or who developed glaucoma after PKP and underwent a surgical procedure to control the glaucoma at the University Eye Associates of Boston University Medical Center, New England Eye Center, and Massachusetts Eye and Ear Infirmary between January 1991 and July 1995 were reviewed. Follow-up ranged from 6 months to 4 years after the glaucoma procedure. A total of 38 patients were included consisting of 17 patients who underwent mitomycin C, 10 patients who underwent GDD surgery, and 11 patients who had CPC. Intervention Mitomycin C trabeculectomy, GDDs, or Nd:YAG CPC to control glaucoma after PKP was performed. Main outcome measures Graft status, postoperative intraocular pressure (IOP), and visual acuity were the main outcome measures. Results There were no differences among the three groups with respect to the follow-up time after the corneal graft operation ( P = 0.15) or after the glaucoma operation ( P = 0.98). At the final follow-up, the average decrease in the IOP was 17 mmHg ( P P = 0.003) after GDD surgery, and 14.4 mmHg ( P = 0.001) after CPC. There were no differences in the proportion of patients who developed postoperative IOP above 20 mmHg ( P = 0.50) and in the proportion who developed hypotony ( P = 0.10) among the three groups. Two grafts failed after mitomycin C and one failed after CPC. Among the three procedures, there were no differences in the proportion of patients who experienced either an improvement ( P = 0.14) or a decrease ( P = 0.22) in the visual acuity by more than one line after the glaucoma procedure. One patient each in the GDD group and the CPC group lost light perception after the procedure. The risk of graft failure was almost three times higher for each additional PKP (odds ratio=2.80, P = 0.02). Conclusions No differences were found among the three glaucoma procedures with respect to controlling IOP and graft failure. There was a trend for patients treated with CPC to have a higher incidence of graft failure, glaucoma failure, hypotony, and visual loss by more than one line, although this was not statistically significant. The number of PKPs was associated with graft failure, independent of the surgical procedure.
Dispersal patterns for hydrothermal plumes in the South Pacific using manganese as a tracer

Abstract Manganese profiles over the spreading axis of the East Pacific Rise (EPR) between 22°15′S and 19°25′S disclose a series of plumes which are formed by buoyant emanations of hot, hydrothermal vent fluids. The plume ceilings, or anomaly maxima, can occur several hundred meters above the sea floor. These plumes are dispersed laterally and are detectable as mid-depth manganese anomalies 2000 km from the spreading axis. Along this section, the plumes are dispersed mainly westward but at 30°S the plumes are advected eastward. The asymmetrical dispersal pattern inferred from these data is coincident with the asymmetrical distribution of metalliferous sediments about the EPR which suggests that plumes, generated by high-temperature venting, play a dominant role in the formation of these sediments.
Efficient 2D FFT implementation on mediaprocessors

We have developed an efficient implementation to compute the 2D fast Fourier transform (FFT) on a new very long instruction word programmable mediaprocessor. Using instruction-level parallelism and a multimedia instruction set, our radix-4 Cooley-Tukey algorithm optimally maps the FFT computation to the processing resources of the Hitachi/Equator's MAP mediaprocessor. We have also achieved more efficient data I/O and lower data transfer time compared to traditional implementations by processing several columns in parallel during the column-wise stage of row-column decomposition. We used a programmable direct memory access engine and a double-buffering scheme in the data cache to perform the computation and the data transfer in parallel. Our implementation resulted in 22.4 ms total execution time for a 512 × 512-point 2D complex FFT, which is faster than previous single-chip programmable or dedicated solutions. The implementations on two other mediaprocessors, the TriMedia TM1100 and the BOPS ManArray, illustrate the importance of the instruction set architecture for achieving high performance and the trend of data I/O becoming the limitation on the 2D FFT performance in newer mediaprocessors.
Lifetime in p -Type Silicon

By using the photoconductive decay method, lifetime is measured as a function of excess electron density in $p$-type silicon over the temperature range 200-400\ifmmode^\circ\else\textdegree\fi{}K. The linear dependence of ${\ensuremath{\tau}}_{n}$ on $\ensuremath{\Delta}n$ expected from the Shockley-Read theory of recombination is not obeyed; instead a much stronger dependence is found with minority carrier densities less than ${10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ than at larger densities. The data are discussed in terms of two separate recombinative levels of the Shockley-Read type of of more complex behavior for a single kind of center.
Advances in refractive surgery. New options expand the scope of corrective procedures.

PREVIEWThe Food and Drug Administration's approval of the excimer laser in 1995 heralded the age of laser refractive surgery in the United States. Since then, other advances in refractive surgery have spurred great public interest in and enthusiasm for these procedures. In this article, the authors review the major types of refractive surgery and discuss their indications, results, and complications.
Sagittal knife cuts in the far-lateral hypothalamus reduce sexual receptivity in female hamsters.

Abstract We have previously shown that hypothalamic knife cuts confined to the sagittal plane lateral to the medial anterior hypothalamus-ventromedial nucleus can disrupt sexual receptivity in female golden hamsters. In the present study we have compared the effects of varying the lateral position of sagittal cuts located at this same rostral-caudal level. Near-lateral (NL) cuts were placed at or just lateral to the fornix, while far-lateral (FL) cuts were placed at the lateral edge of the medial forebrain bundle. Ovariectomized, estradiol benzoate plus progesterone-treated females were given weekly tests for lodosis before and after hypothalamic cuts. Changes in body weight and agonistic behavior were also recorded. Both NL and FL cuts reduced lordosis in response to both manual stimulation and a sexually active male. Postoperatively, it was more difficult to elicit lordosis from these females, and if elicited, the duration of the response was reduced. NL, but not FL, cuts also increased agonistic behavior, and produced obesity. Since both NL and FL cuts severed axons traveling in the region of the supraoptic commissures (SOC), these data support our hypothesis that these SOC connections are critical for sexual receptivity. The SOC carry both efferents and afferents of the ventromedial hypothalamus. Sagittal-plane cuts which interrupt the SOC may disrupt lordosis by cutting either or both types of connection.
Further studies on transformation with single-stranded DNA of Hemophilus influenzae*

Earlier studies on transformations with single-stranded DNA have been extended. The main findings were as follows: (1) Transformations were obtained with alkali- as well as heat-denatured DNA. (2) Dogfish liver nuclease, which preferentially attacks single-stranded DNA, reduced the transforming activity of denatured DNA a hundred times faster than native DNA, while pancreatic DNase inactivated both denatured and native DNA's at approximately equal rates. This evidence provided additional support for the view that transformations with denatured DNA in the low pH system were due to single-stranded DNA. (3) By means of a competition test, it was established that denatured DNA at low pH has a greater affinity for cells than native DNA. On the other hand, as shown previously, denatured DNA at neutral pH has considerably lower affinity than native DNA. (4) Linkage determinations in the denatured system gave essentially the same values as for the native system. (5) A modified assay procedure for denatured DNA was developed which increased the efficiency of transformation with denatured DNA to about 20% of that obtained with native DNA. (6) Interspecific transformations occurred with denatured DNA at frequencies two- to three-fold better than those expected from corresponding transformations with native DNA. These findings suggest that, aside from the uptake mechanism, the process of transformation with native and denatured DNA is probably the same.
Computational Analysis and Optimization of a Chemical Vapor Deposition Reactor with Large-Scale Computing

A computational analysis and optimization is presented for the chemical vapor deposition (CVD) of silicon in a horizontal rotating-disk reactor. A three-dimensional reactor-scale model for the gas flow, heat transfer, and mass transfer in a CVD reactor is coupled to a simple transport-limited surface reaction mechanism for the deposition of epitaxial silicon from trichlorosilane. The model is solved to steady state for the deposition rate profile over the 8-in. silicon wafer using an unstructured-grid finite-element method and a fully coupled inexact Newton method on parallel computers. Because a high degree of spatial uniformity in the deposition rate is desired, parameter continuation runs for six key operating parameters, including the inlet flow rate and the rotation rate of the substrate, were performed and their individual effects analyzed. Finally, optimization runs were performed that located operating conditions that predict nonuniformity as low as 0.1%.
Hydrophobic Chemistry in Aqueous Solution: Stabilization and Stereoselective Encapsulation of Phosphonium Guests in a Supramolecular Host

Encapsulation of guest molecules inside supramolecular host assemblies provides a way to stabilize reactive species in aqueous solution. The stabilization of reactive phosphonium/ketone adducts of the general formula [R1MeC(OH)PR3]+ by encapsulation as guest molecules within a [Ga4L6]12− tetrahedral metal−ligand assembly is reported; although these cations decompose in aqueous solution, encapsulation inside the hydrophobic cavity of the assembly lengthens their lifetimes considerably, in some cases up to weeks. By varying the phosphane (PMe3, PEt3, PPhMe2, and PPh2Me) and ketone (acetone, methyl ethyl ketone, 1,1,1-trifluoroacetone, and fluoroacetone) which form these adducts, as well as the pD of the solutions, it was determined that the pH of the solution as well as the size and shape of the guest cations play an important role in the stability of these host−guest complexes. Encapsulation of chiral guests in the chiral [Ga4L6]12− assembly results in the formation of diastereomers, as characterized by 1H, 19F, and 31P NMR spectroscopy. Although the [Ga4L6]12− assembly is formed from non-chiral ligands, the assembly itself has ΔΔΔΔ or ΛΛΛΛ chirality around the metal centers. Due to the chirality of this assembly, diastereomeric selectivity is observed upon initial guest encapsulation (typical diastereomeric excesses are 30−50%). This initial diastereomeric selectivity decreases over time to reach an equilibrium but does not become 1:1, indicating both kinetic and thermodynamic processes promote selective guest encapsulation. These experiments demonstrate further the applications of nanoscale reaction vessels, self-assembled by design from non-chiral ligands, in providing a chiral and hydrophobic environment for guest molecules in aqueous solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
P3-S7.16 Lactobacillus crispatus colonisation reduces risk of Bacterial Vaginosis (BV) acquisition

Background Longitudinal studies have found that vaginal colonisation by hydrogen peroxide-producing strains of lactobacilli is associated with a reduced risk of BV acquisition. Several Lactobacillus spp. including L crispatus , L jensenii , and L gasseri can produce hydrogen peroxide, but no longitudinal studies to date have assessed whether all hydrogen peroxide producing species are equally protective. The objective of this study was to determine which species of Lactobacillus were associated with a reduced risk of BV acquisition. Methods In this secondary analysis of women enrolled in a vaccine trial, 112 women aged 18–40 who had Gram stain Nugent scores Results There were 40 BV acquisitions detected during 486 follow-up visits over 65.3 woman-years for an incidence of 61 per 100 woman-years. As shown in Abstract P3-S7.16 table 1, women colonised by L crispatus were 53% less likely to acquire BV at a subsequent visit (p=0.023). Conclusions L crispatus was the only species protective against BV acquisition. Since neither L jensenii nor L gasseri reduced the risk of BV despite their capacity to produce hydrogen peroxide, other characteristics of L crispatus may be more critical then peroxide production in protecting from BV acquisition.