cssi/SciSciGPT-SciSciNet huggingface dataset:
The Price of Incentivizing Exploration: A Characterization via Thompson Sampling and Sample Complexity

We consider incentivized exploration: a version of multi-armed bandits where the choice of arms is controlled by self-interested agents, and the algorithm can only issue recommendations. The algorithm controls the flow of information, and the information asymmetry can incentivize the agents to explore. Prior work achieves optimal regret rates up to multiplicative factors that become arbitrarily large depending on the Bayesian priors, and scale exponentially in the number of arms. A more basic problem of sampling each arm once runs into similar factors. We focus on the price of incentives: the loss in performance, broadly construed, incurred for the sake of incentive-compatibility. We prove that Thompson Sampling, a standard bandit algorithm, is incentive-compatible if initialized with sufficiently many data points. The performance loss due to incentives is therefore limited to the initial rounds when these data points are collected. The problem is largely reduced to that of sample complexity: how many rounds are needed? We address this question, providing matching upper and lower bounds and instantiating them in various corollaries. Typically, the optimal sample complexity is polynomial in the number of arms and exponential in the "strength of beliefs".
Neurophysiological Correlates of the Dunning-Kruger Effect

Abstract. The Dunning-Kruger Effect (DKE) is a metacognitive phenomenon of illusory superiority in which individuals who perform poorly on a task believe they performed better than others, yet individuals who performed very well believe they under-performed compared to others. This phenomenon has yet to be directly explored in episodic memory, nor explored for reaction times or physiological correlates. We designed a novel method to elicit the DKE via a test of item recognition while electroencephalography (EEG) was recorded. Throughout the task, participants were asked to estimate the percentile in which they performed compared to others. Results revealed participants in the bottom 25th percentile overestimated their percentile, while participants in the top 75th percentile underestimated their percentile, exhibiting the classic DKE. Reaction time measures revealed a condition x group interaction whereby over-estimators responded faster than under-estimators when estimating being in the top percentile and responded slower when estimating being in the bottom percentile. Between-group EEG differences were evident between over-estimators and under-estimators during Dunning-Kruger responses, which revealed FN400-like effects of familiarity supporting differences for over-estimators from 400-600 ms, whereas ‘old-new’ memory ERP effects revealed a late parietal component (LPC) associated with recollection-based processing from 600-900 ms for under-estimators that was not evident for over-estimators. Findings suggest over- and under-estimators use differing cognitive processes when assessing their performance, such that under-estimators rely on recollection during memory and over-estimators draw upon excess familiarity when over-estimating their performance. Episodic memory thus appears to play a contributory role in metacognitive judgments of illusory superiority and inferiority. Graphical Abstract Event-related potentials (ERPS) were recorded for the Dunning-Kruger Effect as subjects made metacognitive judgments about performance on a memory task. Over- and Under-estimators exhibited a crossover interaction in response times when believing they did best and worst, respectively. A crossover pattern was also observed for ERPs: LPC signals of recollection were found for under-estimators, whereas familiarity-based FN400 effects were evident for over-estimators and correlated with estimates.
The opportunity cost of hedging under incomplete information: Evidence from ETF/Ns

This paper considers the optimal hedge ratio problem under estimation risk. Due to incomplete information, the decision‐maker evaluates the opportunity cost of hedging using exchange‐traded funds or notes (ETF/Ns). Using a backtesting procedure over the last 5 years and 13 different hedging instruments—both inverse‐equity ETFs and volatility ETNs—we quantify the proposed opportunity cost using different out‐of‐sample performance metrics. Given the greater accessibility of commission‐free brokers for small investors along with the popularity of ETF/Ns, our paper appeals to retail investors and provides guidance in terms of choosing the optimal hedge ratio under estimation risk.
Adult stem cell-derived complete lung organoid models emulate lung disease in COVID-19.

Author(s): Tindle, Courtney; Fuller, MacKenzie; Fonseca, Ayden; Taheri, Sahar; Ibeawuchi, Stella-Rita; Beutler, Nathan; Katkar, Gajanan Dattatray; Claire, Amanraj; Castillo, Vanessa; Hernandez, Moises; Russo, Hana; Duran, Jason; Crotty Alexander, Laura E; Tipps, Ann; Lin, Grace; Thistlethwaite, Patricia A; Chattopadhyay, Ranajoy; Rogers, Thomas F; Sahoo, Debashis; Ghosh, Pradipta; Das, Soumita | Abstract: BackgroundSARS-CoV-2, the virus responsible for COVID-19, causes widespread damage in the lungs in the setting of an overzealous immune response whose origin remains unclear.MethodsWe present a scalable, propagable, personalized, cost-effective adult stem cell-derived human lung organoid model that is complete with both proximal and distal airway epithelia. Monolayers derived from adult lung organoids (ALOs), primary airway cells, or hiPSC-derived alveolar type II (AT2) pneumocytes were infected with SARS-CoV-2 to create in vitro lung models of COVID-19.ResultsInfected ALO monolayers best recapitulated the transcriptomic signatures in diverse cohorts of COVID-19 patient-derived respiratory samples. The airway (proximal) cells were critical for sustained viral infection, whereas distal alveolar differentiation (AT2→AT1) was critical for mounting the overzealous host immune response in fatal disease; ALO monolayers with well-mixed proximodistal airway components recapitulated both.ConclusionsFindings validate a human lung model of COVID-19, which can be immediately utilized to investigate COVID-19 pathogenesis and vet new therapies and vaccines.FundingThis work was supported by the National Institutes for Health (NIH) grants 1R01DK107585-01A1, 3R01DK107585-05S1 (to SD); R01-AI141630, CA100768 and CA160911 (to PG) and R01-AI 155696 (to PG, DS and SD); R00-CA151673 and R01-GM138385 (to DS), R01- HL32225 (to PT), UCOP-R00RG2642 (to SD and PG), UCOP-R01RG3780 (to P.G. and D.S) and a pilot award from the Sanford Stem Cell Clinical Center at UC San Diego Health (P.G, S.D, D.S). GDK was supported through The American Association of Immunologists Intersect Fellowship Program for Computational Scientists and Immunologists. L.C.A's salary was supported in part by the VA San Diego Healthcare System. This manuscript includes data generated at the UC San Diego Institute of Genomic Medicine (IGC) using an Illumina NovaSeq 6000 that was purchased with funding from a National Institutes of Health SIG grant (#S10 OD026929).
Topological magnetic textures in magnetic topological insulators

The surfaces of intrinsic magnetic topological insulators (TIs) host magnetic moments exchange-coupled to Dirac electrons. We study the magnetic phases arising from tuning the electron density using variational and exact diagonalization approaches. In the dilute limit, we find that magnetic skyrmions are formed, which bind to electrons, leading to a skyrmion Wigner crystal phase while at higher densities spin spirals accompanied by chiral one-dimensional channels of electrons are formed. The binding of electrons to textures raises the possibility of manipulating textures with electrostatic gating. We determine the phase diagram capturing the competition of intrinsic spin-spin interactions and carrier density and comment on the possible application to experiments in magnetic TIs and spintronic devices such as skyrmion-based memory.
The Picard group of the moduli space of sheaves on a quadric surface

In this paper, we study the Picard group of the moduli space of semistable sheaves on a smooth quadric surface. We polarize the surface by an ample divisor close to the anticanonical class. We focus especially on moduli spaces of sheaves of small discriminant, where we observe new and interesting behavior. Our method relies on constructing certain resolutions for semistable sheaves and applying techniques of geometric invariant theory to the resulting families of sheaves.
Generalized Max-Flows and Min-Cuts in Simplicial Complexes

We consider high dimensional variants of the maximum flow and minimum cut problems in the setting of simplicial complexes and provide both algorithmic and hardness results. By viewing flows and cuts topologically in terms of the simplicial (co)boundary operator we can state these problems as linear programs and show that they are dual to one another. Unlike graphs, complexes with integral capacity constraints may have fractional max-flows. We show that computing a maximum integral flow is NP-hard. Moreover, we give a combinatorial definition of a simplicial cut that seems more natural in the context of optimization problems and show that computing such a cut is NP-hard. However, we provide conditions on the simplicial complex for when the cut found by the linear program is a combinatorial cut. For d-dimensional simplicial complexes embedded into ℝ^{d+1} we provide algorithms operating on the dual graph: computing a maximum flow is dual to computing a shortest path and computing a minimum cut is dual to computing a minimum cost circulation. Finally, we investigate the Ford-Fulkerson algorithm on simplicial complexes, prove its correctness, and provide a heuristic which guarantees it to halt.
Particle-hole symmetry and the reentrant integer quantum Hall Wigner solid

The interplay of strong Coulomb interactions and of topology is currently under intense scrutiny in various condensed matter and atomic systems. One example of this interplay is the phase competition of fractional quantum Hall states and the Wigner solid in the two-dimensional electron gas. Here we report a Wigner solid at ν = 1.79 and its melting due to fractional correlations occurring at ν = 9/5. This Wigner solid, that we call the reentrant integer quantum Hall Wigner solid, develops in a range of Landau level filling factors that is related by particle-hole symmetry to the so called reentrant Wigner solid. We thus find that the Wigner solid in the GaAs/AlGaAs system straddles the partial filling factor 1/5 not only at the lowest filling factors, but also near ν = 9/5. Our results highlight the particle-hole symmetry as a fundamental symmetry of the extended family of Wigner solids and paint a complex picture of the competition of the Wigner solid with fractional quantum Hall states. Two-dimensional electron gases host topological states such as fractional quantum Hall states, which often compete with correlated insulators formed due to Coulomb interactions, such as the Wigner solid. Here the authors report a re-entrant Wigner solid which forms and melts due to fractional correlations, highlighting the role of particle-hole symmetry for phase competition in the quantum Hall regime.
How Does Information Asymmetry Affect REIT Investments? Cost of Capital, Performance, and Executive Compensation

This study empirically examines the impact of information asymmetry on the firm-level investment behaviors using the information on U.S. equity real estate investment trusts (REITs). We show that firms with lower levels of information asymmetry, measured as bid-ask spread and stock return volatility, generally experience higher growth on their real estate investment, property investment, and total assets. Those high information asymmetry REITs are also less active in their property acquisition and disposition activities, as well as involve in fewer mergers and acquisitions. Moreover, the paper provides evidence that the levels of information asymmetry are, on average, positively related to the cost of capital, and negatively related to operational performance. Lastly, the study sheds light on the importance of aligning interests of managers with those of stakeholders, by illustrating that executives in firms with a high level of information asymmetry receive higher total pays compared with their pairs.
A Risk Estimation System to Predict Postpartum Cigarette Smoking Relapse

Postpartum relapse to cigarette smoking (PRS) rate has not substantially improved for more than two decades. Over 55% of women successfully quit smoking during pregnancy; however, half (50%) return to smoking within three months of childbirth and 90% relapse within a year. The identification of effective PRS prevention interventions are needed, especially since factors related to PRS risk factors vary by person, time, and context. In this paper, a prototype risk estimation system using daily ecological momentary assessment data is proposed to develop an adaptive intervention system which will consider multiple risk factors. The risk estimator is designed using a hierarchical fuzzy inference system design scheme to capture human knowledge. A particle swarm optimization scheme is also applied. The simulation results show the feasibility of the proposed estimator for the PRS prevention intervention system.
Efficient and Less Centralized Federated Learning.

With the rapid growth in mobile computing, massive amounts of data and computing resources are now located at the edge. To this end, Federated learning (FL) is becoming a widely adopted distributed machine learning (ML) paradigm, which aims to harness this expanding skewed data locally in order to develop rich and informative models. In centralized FL, a collection of devices collaboratively solve a ML task under the coordination of a central server. However, existing FL frameworks make an over-simplistic assumption about network connectivity and ignore the communication bandwidth of the different links in the network. In this paper, we present and study a novel FL algorithm, in which devices mostly collaborate with other devices in a pairwise manner. Our nonparametric approach is able to exploit network topology to reduce communication bottlenecks. We evaluate our approach on various FL benchmarks and demonstrate that our method achieves 10\(\times \) better communication efficiency and around 8% increase in accuracy compared to the centralized approach.
Ppsim: A Software Package for Efficiently Simulating and Visualizing Population Protocols.

We introduce ppsim [28], a software package for efficiently simulating population protocols, a widely-studied subclass of chemical reaction networks (CRNs) in which all reactions have two reactants and two products. Each step in the dynamics involves picking a uniform random pair from a population of n molecules to collide and have a (potentially null) reaction. In a recent breakthrough, Berenbrink, Hammer, Kaaser, Meyer, Penschuck, and Tran [6] discovered a population protocol simulation algorithm quadratically faster than the naive algorithm, simulating \(\varTheta (\sqrt{n})\) reactions in constant time (independently of n, though the time scales with the number of species), while preserving the exact stochastic dynamics.
Planar Surface Reconstruction From Sparse Views

The paper studies planar surface reconstruction of indoor scenes from two views with unknown camera poses. While prior approaches have successfully created object-centric reconstructions of many scenes, they fail to exploit other structures, such as planes, which are typically the dominant components of indoor scenes. In this paper, we reconstruct planar surfaces from multiple views, while jointly estimating camera pose. Our experiments demonstrate that our method is able to advance the state of the art of reconstruction from sparse views, on challenging scenes from Matterport3D. Project site: this https URL
Stochastic Inflation at NNLO

Stochastic Inflation is an important framework for understanding the physics of de Sitter space and the phenomenology of inflation. In the leading approximation, this approach results in a Fokker-Planck equation that calculates the probability distribution for a light scalar field as a function of time. Despite its successes, the quantum field theoretic origins and the range of validity for this equation have remained elusive, and establishing a formalism to systematically incorporate higher order effects has been an area of active study. In this paper, we calculate the next-to-next-to-leading order (NNLO) corrections to Stochastic Inflation using Soft de Sitter Effective Theory (SdSET). In this effective description, Stochastic Inflation manifests as the renormalization group evolution of composite operators. The leading impact of non-Gaussian quantum fluctuations appears at NNLO, which is presented here for the first time; we derive the coefficient of this term from a two-loop anomalous dimension calculation within SdSET. We solve the resulting equation to determine the NNLO equilibrium distribution and the low-lying relaxation eigenvalues. In the process, we must match the UV theory onto SdSET at one-loop order, which provides a non-trivial confirmation that the separation into Wilson-coefficient corrections and contributions to initial conditions persists beyond tree level. Furthermore, these results illustrate how the naive factorization of time and momentum integrals in SdSET no longer holds in the presence of logarithmic divergences. It is these effects that ultimately give rise to the renormalization group flow that yields Stochastic Inflation.
Dissecting genomic determinants of positive selection with an evolution-guided regression model.

In evolutionary genomics, it is fundamentally important to understand how characteristics of genomic sequences, such as gene expression level, determine the rate of adaptive evolution. While numerous statistical methods, such as the McDonald-Kreitman test, are available to examine the association between genomic features and the rate of adaptation, we currently lack a statistical approach to disentangle the independent effect of a genomic feature from the effects of other correlated genomic features. To address this problem, I present a novel statistical model, the MK regression, which augments the McDonald-Kreitman test with a generalized linear model. Analogous to the classical multiple regression model, the MK regression can analyze multiple genomic features simultaneously to infer the independent effect of a genomic feature, holding constant all other genomic features. Using the MK regression, I identify numerous genomic features driving positive selection in chimpanzees. These features include well-known ones, such as local mutation rate, residue exposure level, tissue specificity, and immune genes, as well as new features not previously reported, such as gene expression level and metabolic genes. In particular, I show that highly expressed genes may have a higher adaptation rate than their weakly expressed counterparts, even though a higher expression level may impose stronger negative selection. Also, I show that metabolic genes may have a higher adaptation rate than their non-metabolic counterparts, possibly due to recent changes in diet in primate evolution. Overall, the MK regression is a powerful approach to elucidate the genomic basis of adaptation.
The Rise and Fall of the Eclipsing Binary HS Hydrae

HS Hydrae is a short period eclipsing binary (P_orb=1.57 day) that belongs to a rare group of systems observed to have rapidly changing inclinations. This evolution is due to a third star on an intermediate orbit, and results in significant differences in eclipse depths and timings year-to-year. Zasche & Paschke (2012) revealed that HS Hydrae's eclipses were rapidly fading from view, predicting they would cease around 2022. Using 25 days of photometric data from Sector 009 of the Transiting Exoplanet Survey Satellite (TESS), we find that the primary eclipses for HS Hydrae were only 0.00173+/-0.00007 mag in depth in March 2019. This data from TESS likely represents the last eclipses detected from HS Hydrae. We also searched the Digitization of the Harvard Astronomical Plate Collection (DASCH) archive for historic data from the system. With a total baseline of over 125 years, this unique combination of data sets - from photographic plates to precision space-based photometry - allows us to trace the emergence and decay of eclipses from HS Hydrae, and further constrain its evolution. Recent TESS observations from Sector 035 confirm that eclipses have ceased for HS Hya, and we estimate they will begin again in 2195.
'Walking Into a Fire Hoping You Don't Catch': Strategies and Designs to Facilitate Cross-Partisan Online Discussions

While cross-partisan conversations are central to a vibrant deliberative democracy, these conversations are hard to have, especially amidst unprecedented levels of partisan animosity we observe today. We report on a qualitative study of 17 US residents who engage with outpartisans on Reddit to understand what they look for in these interactions, and the strategies they adopt. We find that users have multiple, sometimes contradictory expectations of these conversations, ranging from deliberative discussions to entertainment and banter. In aiming to foster 'good' cross-partisan discussions, users make strategic choices on which subreddits to participate in, who to engage with and how to talk to outpartisans, often establishing common ground, complimenting, and remaining dispassionate in their interactions. Further, contrary to offline settings where knowing more about outpartisan interlocutors help manage disagreements, on Reddit, users look to actively learn as little as possible about them for fear that such information may bias their interactions. However, through design probes, we find that users are actually open to knowing certain kinds of information about their interlocutors, such as non-political subreddits that they both participate in, and to having that information made visible to their interlocutors. However, making other information visible, such as the other subreddits that they participate in or their past comments, though potentially humanizing, raises concerns around privacy and misuse of that information for personal attacks especially among women and minority groups. Finally, we identify important challenges and opportunities in designing to improve online cross-partisan interactions in today's hyper-polarized environment.
Universality, Lee-Yang Singularities, and Series Expansions.

We introduce a new way of reconstructing the equation of state of a thermodynamic system near a second-order critical point from a finite set of Taylor coefficients computed away from the critical point. We focus on the Ising universality class (${\mathbb{Z}}_{2}$ symmetry) and show that, in the crossover region of the phase diagram, it is possible to efficiently extract the location of the nearest thermodynamic singularity, the Lee-Yang edge singularity, from which one can (i) determine the location of the critical point, (ii) constrain the nonuniversal parameters that maps the equation of state to that of the Ising model in the scaling regime, and (iii) numerically evaluate the equation of state in the vicinity of the critical point. This is done by using a combination of Pad\'e resummation and conformal maps. We explicitly demonstrate these ideas in the celebrated Gross-Neveu model.
Predictive Runtime Monitoring for Mobile Robots using Logic-Based Bayesian Intent Inference

We propose a predictive runtime monitoring framework that forecasts the distribution of future positions of mobile robots in order to detect and avoid impending property violations such as collisions with obstacles or other agents. Our approach uses a restricted class of temporal logic formulas to represent the likely intentions of the agents along with a combination of temporal logic-based optimal cost path planning and Bayesian inference to compute the probability of these intents given the current trajectory of the robot. First, we construct a large but finite hypothesis space of possible intents represented as temporal logic formulas whose atomic propositions are derived from a detailed map of the robot’s workspace. Next, our approach uses real-time observations of the robot’s position to update a distribution over temporal logic formulae that represent its likely intent. This is performed by using a combination of optimal cost path planning and a Boltzmann noisy rationality model. In this manner, we construct a Bayesian approach to evaluating the posterior probability of various hypotheses given the observed states and actions of the robot. Finally, we predict the future position of the robot by drawing posterior predictive samples using a Monte-Carlo method. We evaluate our framework using two different trajectory datasets that contain multiple scenarios implementing various tasks. The results show that our method can predict future positions precisely and efficiently, so that the computation time for generating a prediction is a tiny fraction of the overall time horizon.
Impact of stratification mechanisms on turbulent characteristics of stable open-channel flows

Flow over a surface can be stratified by imposing a fixed mean vertical temperature (density) gradient profile throughout or via cooling at the surface. These distinct mechanisms can act simultaneously to establish a stable stratification in a flow. Here, we perform a series of direct numerical simulations of open-channel flows to study adaptation of a neutrally stratified turbulent flow under the combined or independent action of the aforementioned mechanisms. We force the fully developed flow with a constant mass flow rate. This flow forcing technique enables us to keep the bulk Reynolds number constant throughout our investigation and avoid complications arising from the acceleration of the bulk flow when a constant pressure gradient approach were to be adopted to force the flow instead. When both stratification mechanisms are active, the dimensionless stratification perturbation number emerges as an external flow control parameter, in addition to the Reynolds, Froude, and Prandtl numbers. We demonstrate that significant deviations from the Monin-Obukhov similarity formulation are possible when both types of stratification mechanisms are active within an otherwise weakly stable flow, even when the flux Richardson number is well below 0.2. An extended version of the similarity theory due to Zilitinkevich and Calanca shows promise in predicting the dimensionless shear for cases where both types of stratification mechanisms are active, but the extended theory is less accurate for gradients of scalar. The degree of deviation from neutral dimensionless shear as a function of the vertical coordinate emerges as a qualitative measure of the strength of stable stratification for all the cases investigated in this study.
Episodic deluges in simulated hothouse climates

Earth’s distant past and potentially its future include extremely warm ‘hothouse’1 climate states, but little is known about how the atmosphere behaves in such states. One distinguishing characteristic of hothouse climates is that they feature lower-tropospheric radiative heating, rather than cooling, due to the closing of the water vapour infrared window regions2. Previous work has suggested that this could lead to temperature inversions and substantial changes in cloud cover3–6, but no previous modelling of the hothouse regime has resolved convective-scale turbulent air motions and cloud cover directly, thus leaving many questions about hothouse radiative heating unanswered. Here we conduct simulations that explicitly resolve convection and find that lower-tropospheric radiative heating in hothouse climates causes the hydrologic cycle to shift from a quasi-steady regime to a ‘relaxation oscillator’ regime, in which precipitation occurs in short and intense outbursts separated by multi-day dry spells. The transition to the oscillatory regime is accompanied by strongly enhanced local precipitation fluxes, a substantial increase in cloud cover, and a transiently positive (unstable) climate feedback parameter. Our results indicate that hothouse climates may feature a novel form of ‘temporal’ convective self-organization, with implications for both cloud coverage and erosion processes. Through an idealized set of simulations, with a model that incorporates key physics, research reveals dramatic swings between massive rainfall events and extended dry periods in hothouse climates.
Inverse Problems Leveraging Pre-trained Contrastive Representations

We study a new family of inverse problems for recovering representations of corrupted data. We assume access to a pre-trained representation learning network R(x) that operates on clean images, like CLIP. The problem is to recover the representation of an image R(x), if we are only given a corrupted version A(x), for some known forward operator A. We propose a supervised inversion method that uses a contrastive objective to obtain excellent representations for highly corrupted images. Using a linear probe on our robust representations, we achieve a higher accuracy than end-to-end supervised baselines when classifying images with various types of distortions, including blurring, additive noise, and random pixel masking. We evaluate on a subset of ImageNet and observe that our method is robust to varying levels of distortion. Our method outperforms end-to-end baselines even with a fraction of the labeled data in a wide range of forward operators.
Physics-informed Dyna-style model-based deep reinforcement learning for dynamic control

Model-based reinforcement learning (MBRL) is believed to have much higher sample efficiency compared with model-free algorithms by learning a predictive model of the environment. However, the perfo...
Instanton and the depth of taut foliations

Sutured instanton Floer homology was introduced by Kronheimer and Mrowka. In this paper, we prove that for a taut balanced sutured manifold with vanishing second homology, the dimension of the sutured instanton Floer homology provides a bound on the minimal depth of all possible taut foliations on that balanced sutured manifold. The same argument can be adapted to the monopole and even the Heegaard Floer settings, which gives a partial answer to one of Juhasz's conjectures. Using the nature of instanton Floer homology, on knot complements, we can construct a taut foliation with bounded depth, given some information on the representation varieties of the knot fundamental groups. This indicates a mystery relation between the representation varieties and some small depth taut foliations on knot complements, and gives a partial answer to one of Kronheimer and Mrowka's conjecture.
Advances in statistical pattern recognition

Statistical pattern recognition is now a mature discipline which has been successfully applied in several application domains. The primary goal in statistical pattern recognition is classification, where a pattern vector is assigned to one of a finite number of classes and each class is characterized by a probability density function on the measured features. A pattern vector is viewed as a point in the multidimensional space defined by the features. Design of a recognition system based on this paradigm requires careful attention to the following issues: type of classifier (single-stage vs. hierarchical), feature selection, estimation of classification error, parametric vs. nonparametric decision rules, and utilizing contextual information. Current research emphasis in pattern recognition is on designing efficient algorithms, studying small sample properties of various estimators and decision rules, implementing the algorithms on novel computer architecture, and incorporating context and domain-specific knowledge in decision making.
Feature Extraction and Coverage Problems in Distributed Sensor Networks

Distributed Sensor Network is a classical area of multi- disciplinary science. This needs a special type of computing, communication and sensing. This talk presents some new results on the following topics: 1) An optimization framework based on mathematical programming for maximizing the coverage probability of a sensor field under the constraints of investment limit; 2) Feature extraction using sensor networks.
Parents' Cultural Belief Systems: Their Origins, Expressions, and Consequences

Parents' Cultural Belief Systems: Their Origins, Expressions, and Consequences. Sara Harkness and Charles M. Super, eds. New York: The Guilford Press, 1996. 558 pp.
Models for compact pulsing X-ray sources.

Cen X-3 is probably a neutron star, releasing the infall energy of accreted matter. Sufficient material for accretion will be provided by a conventional stellar wind from its more massive companion star. That star is not likely to rotate synchronously; therefore a ‘Roche lobe’ analysis of the eclipses is not valid. A ‘tidal lobe’ analysis allows the neutron star to have a mass of the order of one solar mass. Overflow of the ‘Roche lobe’ is neither necessary as a source of mass nor probable in view of the observed stellar line widths of the two identified X-ray companions.
Supporting insertions and deletions in striped parallel filesystems

The dramatic improvements in the processing rates of parallel computers are turning many compute-bound jobs into IO-bound jobs. Parallel file systems have been proposed to better match IO throughput to processing power. Many parallel file systems stripe files across numerous disks; each disk has its own controller. A striped file can be appended (or prepended) to and maintain its structure. However, a block can't be inserted into or deleted from the middle of the file, since this would destroy the round robin striping structure of the file. The author presents a distributed file structure that maintains files in indexed striped extents on a message passing multiprocessor. This approach allows highly parallel random and sequential reads, and also allows insertion and deletion into the middle of the file. >
The Embedded Curator: Reexamining the Documentation Strategy of Archival Acquisitions in a Web 2.0 Environment

An embedded curator uses his or her physical and virtual presence within a selected community to document that community while simultaneously serving as a resource to it. While the “embedded curator” term may be relatively new to the profession, the practices that inform its implementation are not. Collection development for special collections, particularly for archival materials, has a robust history of debate about the best methods for encouraging and managing gifts. 1 Embedded curators require a pragmatic and flexible written collection development policy that values occasional serendipitous acquisitions, as well as a strategic plan to build ongoing collections that focus on . . .
Latent Infection and the Elusive Cytomegalovirus

Herpesviruses characteristically establish latent infections in their hosts. In some instances, the tissue sites or even the specific cells that harbor dormant virus have been identified experimentally. However, the sites of cytomegalovirus (CMV) latency have been difficult to define experimentally in humans, even though epidemiologic evidence indicates that undetectable virus can be transferred from donor to recipient in transfused blood or a transplanted organ. Recently, DNA of human CMV has been found in peripheral blood leukocytes and in normal or malignant colonic tissue by hybridization methods. Studies in mice strongly implicate splenic B lymphocytes as cellular reservoirs of latent CMV; however, the virus may also persist in the salivary glands, the prostate, the testes, peripheral blood, and possibly macrophages. Whether latent CMV infection in these tissues is maintained in a single ubiquitous cell type (e.g., lymphocytes or macrophages) or in various cell types is not known. Definition of the sites and mechanisms involved in the maintenance of latent CMV is essential for a thorough understanding of the pathogenesis of CMV infection. Now that trials with live CMV vaccine have begun, further investigations of latent CMV infection in humans and in animal models are clearly needed.
EventRank: a framework for ranking time-varying networks

Node-ranking algorithms for (social) networks do not respect the sequence of events from which the network is constructed, but rather measure rank on the aggregation of all data. For data sets that relate to the flow of information (e.g., email), this loss of information can obscure the true relative importances of individuals in the network. We present EventRank, a framework for ranking algorithms that respect event sequences and provide a natural way of tracking changes in ranking over time. We compare the performance of a number of ranking algorithms using a large organizational data set consisting of approximately 1 million emails involving over 600 users, including an evaluation of how the email-based ranking correlates with known organizational hierarchy.
Existence of the S-matrix in quantum field theory in curved space-time☆

The existence of the S-matrix is proven for particle creation by an external gravitational field of compact support. No infrared divergences occur even for massless quantum fields; in particular, a localized gravitational field always produces a finite expected total number of particles. The results of this paper apply to both boson and fermion fields as well as to more general linear, external potential interactions.
Comparison of cytoplasmic and mitochondrial 4 S RNA from cultured hamster cells: physical and metabolic properties.

Abstract Gel-electrophoretic, centrifugal and metabolic properties of the low molecular weight (“4 s”) mitochondrial RNA from cultured hamster cells have been compared with those of the corresponding cytoplasmic RNA fraction. On high-resolution acrylamide gel analysis the total 4 s RNA associated with the mitochondrial fraction ran as a single major peak. However, when “endogenous” (ethidium bromide-sensitive) mitochondrial patterns were constructed by subtracting the small amounts of contaminating cytoplasmic RNA present, a second discrete peak was observed, constituting approximately 3% of the ethidium-sensitive 4 s RNA, and migrating slightly beyond the main peak. No mitochondrial fraction with mobility resembling cytoplasmic 5 s RNA was detected. Mixed-labeling studies showed that the main mitochondrial 4 s component could be distinguished from cytoplasmic transfer RNA both by average mobility in gels and by sedimentation rate through sucrose gradients. The direction of the electrophoretic difference was a function of amperage, presumably reflecting differential effects of temperature on conformation. However, mitochondrial 4 s RNA consistently sedimented slower than cytoplasmic RNA, at both 5°C and 23°C, and under native or denaturing conditions. The centrifugal studies yielded an estimated average molecular weight for mitochondrial transfer RNA of 19,000. Studies involving short pulses and pulse-chases indicated that the mode of maturation of mitochondrial transfer RNA was qualitatively different from that of cytoplasmic transfer RNA. Under conditions in which as much as 75% of the 4 s label of the cytoplasmic fraction ran in gels as transfer RNA precursors, the corresponding pulse-labeled mitochondrial RNA migrated with mature transfer RNA.
On the Merits and Demerits of Integer Goal Programming

In a recent paper, it was suggested that the use of integer goal programming is questionable. No mathematical proof was provided to substantiate such a serious and far-reaching claim; instead, several ‘counterexamples’ were presented in support of the allegations. In this paper, we present a refutation of these allegations, and examine the reasons why such erroneous conclusions might have been reached.
Patterns and correlates of depression in hospitalized older adults

Depression is often associated with illness or injury requiring acute hospitalization, particularly in older adults. We sought to determine patterns of change in depressive symptoms in older adults from hospitalization to 3 months post discharge and to examine factors associated with depressive symptoms 3 months after discharge. The study included 197 patients aged 65 years or older hospitalized with an acute medical illness. Sociodemographic and clinical measures, including depressive symptoms using the Center for Epidemiologic Study—Depression (CES-D) scale, were collected during the inpatient stay and at 3 months post discharge. Mean age was 75.3 ± 7.5 (±S.D.) years, 59% of the participants were female, 61% unmarried, and 72% had a high school education or more. High depressive symptoms (i.e., CES-D ≥ 16) were reported in 37% at admission. Of the 8% depressed at follow-up, 81% were also depressed at admission; 19% were new cases of depression. Depressive symptoms 3 months post-hospitalization were significantly associated with follow-up daily living skills (p = 0.001) and social support (p < 0.0001). Patients with persistent depressive symptoms make up the majority of post-hospitalization depression cases. Post-hospitalization social support and daily living skills appear to be important in the management of follow-up depressive symptoms.
Automorphisms of the orthogonal group of a defective space

In a previous paper we determined the automorphisms of the orthogonal groups O(V), O+(V), Q(V), and O’(V) of a non-defective finite dimensional quadratic space L’ over a field F of characteristic 2. The underlying assumptions in [l] were that F had more than 2 elements and that the dimension of V be at least 10. In this paper we remove the assumption of nondefectiveness and investigate the automorphisms of the full orthogonal group O(v). Our main theorem (4.4 in Section 4) is of the type one expects in this situation. Our assumptions include a dimension assumption on the dimension of “the” underlying non-defective part of L’ (that it be at least 6) and an assumption on F. The assumption on F is weak enough to include the case of perfect fields, algebraically closed fields, local fields, and global fields-in fact it includes any field where Q(V*) intersects any ternary F2 subspace of F non-trivially. In particular it is weak enough to be able to derive as a corollary the well-known result concerning automorphisms of the symplective groups Q,,(F), where 2m > 6 and [F: F2] is finite. Our approach utilizes the supply of transvections in O(v). Subject to the conditions mentioned above we show that automorphisms of O(V) carry transvections to transvections. This enables us to produce a bijection of lines to which the Fundamental Theorem of Projective Geometry may be applied. The form of the automorphism is then readily obtained.
Continuous amino acid analysis: Elution programming and automatic column selection by means of a rotating valve

Abstract The introduction of a system of two rotary valves to automatic amino acid analysis allows the continuous unattended performance of six complete analyses every 24 hr. One of the valves is used to regulate the stepwise 4-buffer elution program while the other valve controls the column selection. Automatic sample application and column regeneration are part of the elution program.
Inwardly rectifying single-channel and whole cell K+ currents in rat ventricular myocytes.

The voltage-dependent properties of inwardly rectifying potassium channels were studied in adult and neonatal rat ventricular myocytes using patch voltage-clamp techniques. Inward rectification was pronounced in the single-channel currentvoltage relation and outward currents were not detected at potentials positive to the calculated reversal potential for potassium (E k). Single-channel currents having at least three different conductances were observed and the middle one was predominant. Its single-channel conductance was nonlinear ranging from 20 to 40 pS. Its open-time distribution was fit by a single exponential and the time constants decreased markedly with hyperpolarization fromE k. The distribution of the closed times required at least two exponentials for fitting, and their taus were related to the bursting behavior displayed at negative potentials. The steady-state probability of being open (P o) for this channel was determined from the single-channel records; in symmetrical isotonic K solutionsP o was 0.73 at −60 mV, but fell to 0.18 at −100 mV. The smaller conductance was about one-half the usual value and the open times were greatly prolonged. The large conductance was about 50 percent greater than the usual value and the open times were very brief. TheP o(V) relation, the kinetics and the conductance of the predominant channel account for most of the whole cell inwardly rectifying current. The kinetics suggest that an intrinsic K+-dependent mechanism may control the gating, and the conductance of this channel. In the steady state, the opening and closing probabilities for the two smaller channels were not independent of each other, suggesting the possibility of a sub-conductance state or cooperativity between different channels.
On the possible functional role of afferent pathways in skin sensation.

Abstract Single unit activity was recorded from postcentral gyrus (SI) neurons in chronically prepared macaque monkeys. Lesions of the dorsal funiculi (especially cuneatus), or the lateral lemniscus (at the mesencephalic level) failed to significantly modify the properties of the cortical responses to peripheral stimuli, while combined lesions of both pathways were quite effective in this regard. An additional finding was that combined “deafferentation” of a hemisphere caused a significant proportion of cells in it to respond to ipsilateral stimuli. We conclude that both the medial lemniscal and spinothalamic pathways carry information—in parallel—to the cortex, that this information is conveyed in two modes by each pathway (“elemental” and “convergent”) and that ipsilateral inputs relayed to SI are revealed by partial deafferentation of its contralateral inputs.
The administration of pharmacological doses of testosterone or 19-nortestosterone to normal men is not associated with increased insulin secretion or impaired glucose tolerance

Excess androgen secretion and exogenous androgen administration may decrease insulin sensitivity and impair glucose tolerance. We examined the responses to an oral glucose tolerance test in 30 normal men before and after 6 weekly injections of androgen administered in a double-blinded study design. The men were randomly assigned to 1 of 4 treatment groups: testosterone enanthate (TE), 100 or 300 mg/week, or 19-nortestosterone decanoate (ND), 100 or 300 mg/week. Serum testosterone levels, measured 2-3 days after the last dose, did not change in the men given 100 mg TE/week, increased 3-fold in those given 300 mg TE/week, and decreased in both ND groups. All four groups had comparable reductions in serum LH levels. Weight increased significantly in all except the 100 mg TE/week group, but there was no change in waist to hip ratio in any group. In spite of the demonstrated biological effects of the doses of steroid administered, androgen administration for 6 weeks did not increase fasting serum glucose or insulin concentrations. There was also no increase in peak serum insulin levels and areas under the insulin and glucose response curves after a 100-g oral glucose load. However, the mean serum insulin area under the curve decreased significantly in the men given 300 mg ND/week. In contrast to the results of studies of 17-alkylated androgens, our results demonstrate that pharmacological doses of testosterone and the administration of 19-nortestosterone for 6 weeks do not impair glucose tolerance or alter insulin secretion in normal men.