cssi/SciSciGPT-SciSciNet huggingface dataset:
Hedge Funds as Liquidity Providers: Evidence from the Lehman Bankruptcy

Abstract Hedge funds using Lehman as prime broker faced a decline in funding liquidity after the September 15, 2008 bankruptcy. We find that stocks held by these Lehman-connected funds experienced greater declines in market liquidity following the bankruptcy than other stocks; the effect was larger for ex ante illiquid stocks and persisted into the beginning of 2009. We find no similar effects surrounding the Bear Stearns failure, suggesting that disruptions surrounding bankruptcy explain the liquidity effects. We conclude that shocks to traders' funding liquidity reduce the market liquidity of the assets that they trade.
Performance evaluation with high moments and disaster risk

Abstract Traditional performance evaluation measures do not account for tail events and rare disasters. To address this issue, we reinterpret the riskiness measures of Aumann and Serrano (2008) and Foster and Hart (2009) as performance indices. We derive the moment properties of these indices and their sensitivity to rare disasters and show that they are consistent with the asset pricing literature. As applications, we show that “anomalous” investment strategies such as “momentum” or investment in private equity lose much of their glamour when accounting for high moments and rare events. Furthermore, using the indices to select mutual funds results in desirable high-moment properties out of sample.
The Egyptian Second Republic: The Future of Litigating Islam Before the Supreme Constitutional Court

This article explores the future of litigating Islam in the Egyptian Second Republic. In particular it discusses the role that the Supreme Constitutional Court of Egypt can play in paving the way for a pluralistic understanding of Islam after the Arab Spring. While reviewing the constitutionality of the legislation, the Court’s interpretation of the Shari’a Clause and how it will affect the legal system will be vital in defining the relationship between Islam and the state and what role Islam will play in the public sphere. This article explores how litigating Islam before the SCC will reveal a form of governance that is neither secular (as in Turkey) nor theocratic (as in Iran). Rather, it will reveal a civic state with an Islamic identity that is based in Intell-political Islam rather than theo-political Islam.
The Defense of Necessity and Powers of the Government

If one of the lessons of the ubiquitous and highly problematic “ticking bomb” scenario is that torture may be justified under certain narrowly specified situations, why would we not want it made available as a weapon in the government’s anti-terrorist activities? This is not a new question. It has been hotly debated, and a number of arguments have been made against the idea of formulating the torture policy on the basis of the ticking-bomb hypothetical. The question that this Essay addresses is related but narrower: if one starts from the proposition that the ticking bomb scenario demonstrates that a government official facing prosecution for torture may have available the necessity defense, what implications, if any, should the government be able to draw from the existence of the defense as it formulates its torture policy? This Essay discusses, and rejects, one common answer to this question—that the nature of the necessity defense is such that it can generate no forward-looking prescriptions. This Essay then advances a new argument on the basis of the nature and function of the necessity defense as not only spelling out morally permissible instances of harm infliction but also effecting a division of power between the state and citizens.
Growth Effects of Free Trade under Increasing Returns

This paper addresses the long-term sustainability of the growth effects from trade, within the context of a dynamic optimization model where the investment sector exhibits an initial phase of increasing returns. It is proved that the qualitative properties of trade and growth remain valid, even for decreasing, rather than constant, returns to scale in the consumption sector. That is, trade enables an economy to escape a “poverty trap” and enjoy unbounded growth. Moreover, the asymptotic long-run growth rate of the optimal consumption levels with trade is determined, establishing that trade has a beneficial effect on long-run growth. JEL Classification Numbers: O41, F12.
Investigating the economic role of mergers

Abstract We investigate the economic role of mergers by performing a comparative study of mergers and internal corporate investment at the industry and firm levels. We find strong evidence that merger activity clusters through time by industry, whereas internal investment does not. Mergers play both an “expansionary” and “contractionary” role in industry restructuring. During the 1970s and 1980s, excess capacity drove industry consolidation through mergers, while peak capacity utilization triggered industry expansion through non-merger investments. In the 1990s, this phenomenon is reversed, as industries with strong growth prospects, high profitability, and near capacity experience the most intense merger activity.
The Revenue Demands of Public Employee Pension Promises

Abstract We calculate increases in contributions required to achieve full funding of state and local pension systems in the United States over 30 years. Without policy changes, contributions would have to increase by 2.5 times, reaching 14.1 percent of the total own revenue generated by state and local governments. This represents a tax increase of $1,385 per household per year, around half of which would go to pay down legacy liabilities while half would fund the cost of new promises. We examine sensitivity to asset return assumptions, wage correlations, the treatment of workers not currently in Social Security, and endogenous geographical shifts in the tax base. (JEL H55, H75, J26, J45)
Acquiring financial resources to form new ventures: the impact of personal characteristics on organizational emergence

Conventional wisdom says that friends, family, and fools provide startup financing. Beyond this platitude, little evidence is available about who acquires precisely what sources of financing during the earliest stages of starting a venture. This study argues for a more nuanced view of the financing of emerging firms that extends prior research on large businesses and small- and medium-sized enterprises. Drawing on human capital and pecking order theory, this study finds that nascent entrepreneurs in the process of creating an organization follow paths of least resistance when acquiring financial resources, which differ according to the entrepreneur's race, as well as firm and industry characteristics.
The New Wittgensteinians and the End of Jurisprudence

This article seeks to critically evaluate the new approach to jurisprudence and legal justification. In particular, one of the most significant contributions of the article is that it seeks to evaluate the new approach by, among other things, examining the history of the Wittgensteinian descriptive project in other areas of philosophy. The article focuses primarily on the work of Philip Bobbitt who has offered the leading example of this type of neo-Wittgensteinian approach. The arguments generated in the course of the article, however, may be applied against any neo-Wittgensteinian internalist approach to jurisprudence. Thus, the article seeks to provide a general critique of the neo-Wittgensteinian internalist project in law.Part II sets out a brief account of Wittgenstein's later approach to philosophy. It also explains that Wittgenstein influenced philosophers to take the linguistic turn. Thus, it describes the approaches of the ideal language philosophers and the ordinary language philosophers.Part II then locates Bobbitt's project within the Wittgensteinian tradition and sets out Bobbitt's basic descriptive approach to jurisprudence. Part II closes by contrasting internal with external approaches to jurisprudence. Part III sets out some alternatives to the internalist descriptive project. Part IV seeks to evaluate the neo-Wittgensteinian internalist descriptive approach to jurisprudence. The article concludes that the neo-Wittgensteinian project should be rejected.
Uncertainty and debt covenants

I examine the use of financial covenants when contracting for debt under uncertainty. Uncertainty, in the context of this study, is a lack of information about future economic events and their consequences for the borrower’s creditworthiness. I examine the implications of ex ante uncertainty that is resolved by information received following loan initiation but prior to maturity. I argue that financial covenants, by transferring control rights ex post, provide a trigger for creditor-initiated renegotiation when the borrower is revealed to be of low credit quality. Using a large sample of private loans, I predict and find that financial covenant intensity is associated with greater uncertainty. I also revisit the agency-based explanation for covenant use and find that this uncertainty explanation is robust to various controls for agency conflicts.
You can take it with you: Proposition 13 tax benefits, residential mobility, and willingness to pay for housing amenities ☆

Abstract The endogeneity of prices has long been recognized as the main identification problem in the estimation of marginal willingness to pay (MWTP) for the characteristics of a given product. This issue is particularly important in the housing market, since a number of housing and neighborhood features are unobserved by the econometrician. This paper proposes the use of a well defined type of transaction costs–moving costs generated by property tax laws–to deal with this type of omitted variable bias. California's Proposition 13 property tax law is the source of variation in transaction costs used in the empirical analysis. Beyond its fiscal consequences, Proposition 13 created a lock-in effect on housing choice because of the implicit tax break enjoyed by homeowners living in the same house for a long time. Its importance to homeowners is estimated from a natural experiment created by two amendments that allow households headed by an individual over the age of 55 to transfer the implicit tax benefit to a new home. Indeed, 55-year old homeowners have 25% higher moving rates than those of comparable 54 year olds. These transaction costs from the property tax laws are then incorporated into a household sorting model. The key insight is that because of the property tax laws, different potential buyers may have different user costs for the same house. The exogenous property tax component of this user cost is then used as an instrumental variable. I find that MWTP estimates for housing characteristics are approximately 100% upward biased when the choice model does not account for the price endogeneity.
Relative Wealth Concerns and Financial Bubbles

We present a rational general equilibrium model that highlights the fact that relative wealth concerns can play a role in explaining financial bubbles. We consider a finite-horizon overlapping generations model in which agents care only about their consumption. Though the horizon is finite, competition over future investment opportunities makes agents' utilities dependent on the wealth of their cohort and induces relative wealth concerns. Agents herd into risky securities and drive down their expected return. Even though the bubble is likely to burst and lead to a substantial loss, agents' relative wealth concerns make them afraid to trade against the crowd.
Path Dependence in Discrimination Law: Employment Cases in the United States and the European Union

Race analogies are a staple of U.S. anti-discrimination advocacy. However, many worry that race precedents have made U.S. equality law overly formalistic and have blocked sex, disability, age and sexual orientation claims that do not fit neatly into the race-blindness paradigm. Are race precedents severe constraints? Or are they malleable tools? To date, examining the U.S. historical record has not led to a clear answer, or allowed for the development of a practicable alternative to the race-blindness model. Few comparative evidence sheds light on these questions. The European Court of Justice (ECJ) developed sex discrimination case law over four decades, and recently decided its first race, age, disability and sexual orientation claims (2006-2009).This Article argues that the sequence in which courts adjudicate claims is an important determinant of the doctrines they develop, and shapes the success and failure of claims subsequent groups bring. The U.S./EU comparison reveals that departing from race-blindness is a double-edged sword. EU equality law offers greater protections to individuals who make claims that courts consider group-typical (e.g., women seeking flexible schedules to take care of children). In contrast, U.S. law benefits atypical workers (e.g., older workers seeking to work past conventional retirement ages). Path dependence arguments show that social movements have substantial opportunities to influence court decisions early on. Once doctrine solidifies, activists are more successful if they redirect efforts away from courts, and towards legislatures and employers.
Texting While Driving Meets the Fourth Amendment: Deterring Both Texting and Warrantless Cell Phone Searches

Recent laws criminalizing texting while driving are under-inclusive, ambiguous, and impose light punishments that are unlikely to deter. At the same time, the laws empower police to conduct warrantless searches of drivers’ cell phones. Texting while driving is dangerous and should be punished with stiff fines, possible jail time, license suspensions, and interlock devices that prevent use of phones while driving. However, more severe punishment will not eliminate police authority to conduct warrantless cell phone searches. This Article therefore proposes that legislatures allow drivers to immediately confess to texting while driving in exchange for avoiding a search of their phones. Trading a confession for a search will encourage guilty pleas while reducing invasive, warrantless cell phone searches that are currently authorized under the Fourth Amendment.
Too much of a good thing?: The proactive response dilemma

In a two-player proactive response game the level of proactive activity and the choice of terrorist target is endogenized. The targeted government first chooses its measures to weaken the terrorists, and the terrorists then choose the type of event—normal or spectacular. Unlike previous analyses, proactive policy has a downside by increasing grievances and, consequently, terrorist recruitment. If the government responds too harshly, its actions can empower the terrorists by providing a larger constituency. Aggressive antiterrorist actions, encouraged by a high perceived loss from terrorism and low marginal proactive costs, may result in spectacular events with dire consequences. If spectaculars are transferred abroad to soft targets, then proactive operations may be excessive from a global viewpoint as external costs are ignored. The analysis explains why some target nations engage in a modest level of offense but a prime target chooses a large level.
Capital Mobility In A Second–Best World: Moral Hazard With Costly Financial Intermediation

The paper studies financial integration in the presence of moral hazard, where banks may mitigate excessive risk by costly monitoring. The author shows that a drop in banks’ cost of funds, less efficient intermediation technology, higher macroeconomic volatility, and a more generous deposit insurance raise the riskiness of projects in a competitive equilibrium. Overborrowing would arise even in the absence of deposit insurance in circumstances where the cost of risk monitoring is high, the banks’ cost of funds is relatively low, and macroeconomic volatility is high. Reforming an inefficient banking system and improving its operation is a precondition for successful financial integration.
A Simple DNA Handle Attachment Method for Single Molecule Mechanical Manipulation Experiments

Manipulating single molecules and systems of molecules with mechanical force is a powerful technique to examine their physical properties. Applying force requires attachment of the target molecule to larger objects using some sort of molecular tether, such as a strand of DNA. DNA handle attachment often requires difficult manipulations of the target molecule, which can preclude attachment to unstable, hard to obtain, and/or large, complex targets. Here we describe a method for covalent DNA handle attachment to proteins that simply requires the addition of a preprepared reagent to the protein and a short incubation. The handle attachment method developed here provides a facile approach for studying the biomechanics of biological systems.
Postbuckling Behavior of Flat Plates

Results obtained by various investigators of postbuckling behavior are summarized; effect of postbuckling behavior of plates on overall buckling strength of columns and beams; concept of effective width and crippling strength are illustrated by results of test of thin-walled compression member; methods of treating postbuckling strength of flat plates in specifications for structures. (32 refs.)
Telemanipulation with Chopsticks: Analyzing Human Factors in User Demonstrations

Chopsticks constitute a simple yet versatile tool that humans have used for thousands of years to perform a variety of challenging tasks ranging from food manipulation to surgery. Applying such a simple tool in a diverse repertoire of scenarios requires significant adaptability. Towards developing autonomous manipulators with comparable adaptability to humans, we study chopsticks-based manipulation to gain insights into human manipulation strategies. We conduct a within-subjects user study with 25 participants, evaluating three different data-collection methods: normal chopsticks, motion-captured chopsticks, and a novel chopstick telemanipulation interface. We analyze factors governing human performance across a variety of challenging chopstick-based grasping tasks. Although participants rated teleoperation as the least comfortable and most difficult-to-use method, teleoperation enabled users to achieve the highest success rates on three out of five objects considered. Further, we notice that subjects quickly learned and adapted to the teleoperation interface. Finally, while motion-captured chopsticks could provide a better reflection of how humans use chopsticks, the teleoperation interface can produce quality on-hardware demonstrations from which the robot can directly learn.
KRAS interaction with RAF1 RAS-binding domain and cysteine-rich domain provides insights into RAS-mediated RAF activation.

The first step of RAF activation involves binding to active RAS, resulting in the recruitment of RAF to the plasma membrane. To understand the molecular details of RAS-RAF interaction, we present crystal structures of wild-type and oncogenic mutants of KRAS complexed with the RAS-binding domain (RBD) and the membrane-interacting cysteine-rich domain (CRD) from the N-terminal regulatory region of RAF1. Our structures reveal that RBD and CRD interact with each other to form one structural entity in which both RBD and CRD interact extensively with KRAS. Mutations at the KRAS-CRD interface result in a significant reduction in RAF1 activation despite only a modest decrease in binding affinity. Combining our structures and published data, we provide a model of RAS-RAF complexation at the membrane, and molecular insights into RAS-RAF interaction during the process of RAS-mediated RAF activation. The molecular details of the RAS-RAF interaction are still not fully understood. Here, the authors present crystal structures of wild-type and mutant KRAS in complex with the RAS-binding and membrane-interacting cysteine-rich domains of RAF1, and propose a model of the membrane-bound RAS-RAF complex.
The McdAB system positions α‐carboxysomes in proteobacteria

Carboxysomes are protein-based organelles essential for carbon fixation in cyanobacteria and proteobacteria. Previously, we showed that the cyanobacterial nucleoid is used to equally space out β-carboxysomes across cell lengths by a two-component system (McdAB) in the model cyanobacterium Synechococcus elongatus PCC 7942. More recently, we found that McdAB systems are widespread among β-cyanobacteria, which possess β-carboxysomes, but are absent in α-cyanobacteria, which possess structurally and phyletically distinct α-carboxysomes. Cyanobacterial α-carboxysomes are thought to have arisen in proteobacteria and then horizontally transferred into cyanobacteria, which suggests that α-carboxysomes in proteobacteria may also lack the McdAB system. Here, using the model chemoautotrophic proteobacterium Halothiobacillus neapolitanus, we show that a McdAB system distinct from that of β-cyanobacteria operates to position α-carboxysomes across cell lengths. We further show that this system is widespread among α-carboxysome-containing proteobacteria and that cyanobacteria likely inherited an α-carboxysome operon from a proteobacterium lacking the mcdAB locus. These results demonstrate that McdAB is a cross-phylum two-component system necessary for positioning both α- and β-carboxysomes. The findings have further implications for understanding the positioning of other protein-based bacterial organelles involved in diverse metabolic processes. PLAIN LANGUAGE SUMMARY: Cyanobacteria are well known to fix atmospheric CO2 into sugars using the enzyme Rubisco. Less appreciated are the carbon-fixing abilities of proteobacteria with diverse metabolisms. Bacterial Rubisco is housed within organelles called carboxysomes that increase enzymatic efficiency. Here we show that proteobacterial carboxysomes are distributed in the cell by two proteins, McdA and McdB. McdA on the nucleoid interacts with McdB on carboxysomes to equidistantly space carboxysomes from one another, ensuring metabolic homeostasis and a proper inheritance of carboxysomes following cell division. This study illuminates how widespread carboxysome positioning systems are among diverse bacteria. Carboxysomes significantly contribute to global carbon fixation; therefore, understanding the spatial organization mechanism shared across the bacterial world is of great interest.
How to Sell Information Optimally: An Algorithmic Study

We investigate the algorithmic problem of selling information to agents who face a decision-making problem under uncertainty. We adopt the model recently proposed by Bergemann et al. [Bergemann et al., 2018], in which information is revealed through signaling schemes called experiments. In the single-agent setting, any mechanism can be represented as a menu of experiments. Our results show that the computational complexity of designing the revenue-optimal menu depends heavily on the way the model is specified. When all the parameters of the problem are given explicitly, we provide a polynomial time algorithm that computes the revenue-optimal menu. For cases where the model is specified with a succinct implicit description, we show that the tractability of the problem is tightly related to the efficient implementation of a Best Response Oracle: when it can be implemented efficiently, we provide an additive FPTAS whose running time is independent of the number of actions. On the other hand, we provide a family of problems, where it is computationally intractable to construct a best response oracle, and we show that it is NP-hard to get even a constant fraction of the optimal revenue. Moreover, we investigate a generalization of the original model by Bergemann et al. [Bergemann et al., 2018] that allows multiple agents to compete for useful information. We leverage techniques developed in the study of auction design (see e.g. [Yang Cai et al., 2012; Saeed Alaei et al., 2012; Yang Cai et al., 2012; Yang Cai et al., 2013; Yang Cai et al., 2013]) to design a polynomial time algorithm that computes the revenue-optimal mechanism for selling information.
FDI Protectionism Is on the Rise

Over the past two decades or so, countries have liberalized their FDI regulatory frameworks and have put in place an international investment law regime that provides various protections for international investors. In the past few years, however, there are signs that countries are reevaluating their approach toward such investment. As a result, FDI protectionism is on the rise, with screening of inward M&As becoming more frequent. Typically, this is being done under the guise of national interest or similar concepts, often linked to strategic sectors and national champions. While the international investment law regime faces a challenge to find the right balance between the rights and responsibilities of governments and investors, care needs to be taken that the rise of FDI protectionism does not endanger a rules-based approach to FDI. An independent FDI Protectionism Observatory to monitor new protectionist measures and name and shame countries that take them is therefore needed.
Digital herd immunity and COVID-19.

A population can be immune to epidemics even if not all of its individual members are immune to the disease, so long as sufficiently many are immune-this is the traditional notion of herd immunity. In the smartphone era a population can be immune to epidemicseven if not a single one of its members is immune to the disease-a notion we call "digital herd immunity'', which is similarly an emergent characteristic of the population. This immunity arises because contact-tracing protocols based on smartphone capabilities can lead to highly efficient quarantining of infected population members and thus the extinguishing of nascent epidemics. When the disease characteristics are favorable and smartphone usage is high enough, the population is in this immune phase. As usage decreases there is a novel "contact-tracing phase transition'' to an epidemic phase. We present and study a simple branching-process model for COVID-19 and show that digital immunity is possible regardless of the proportion of non-symptomatic transmission.
Generator Parameter Estimation by Q-Learning Based on PMU Measurements

In this paper, a novel Q-learning based approach is proposed for estimating the parameters of synchronous generators using PMU measurements. Event playback is used to generate model outputs under different parameters for training the agent in Q-learning. We assume that the exact values of some parameters in the model are not known by the agent in Q-learning. Then, an optimal history-dependent policy for the exploration-exploitation trade-off is planned. With given prior knowledge, the parameter vector can be viewed as states with a specific reward, which is a function of the fitting error compared with the measurements. The agent takes an action (either increasing or decreasing the parameter) and the estimated parameter will move to a new state. Based on the reward function, the optimal action policy will move the parameter set to a state with the highest reward. If multiple events are available, they will be used sequentially so that the updated Q-value can be utilized to improve the computational efficiency. The effectiveness of the proposed approach is validated through estimating the parameters of the dynamic model of a synchronous generator.
Quantum Sensing of Insulator‐to‐Metal Transitions in a Mott Insulator

Nitrogen vacancy (NV) centers, optically-active atomic defects in diamond, have attracted tremendous interest for quantum sensing, network, and computing applications due to their excellent quantum coherence and remarkable versatility in a real, ambient environment. Taking advantage of these strengths, we report on NV-based local sensing of the electrically driven insulator-to-metal transition (IMT) in a proximal Mott insulator. We studied the resistive switching properties of both pristine and ion-irradiated VO2 thin film devices by performing optically detected NV electron spin resonance measurements. These measurements probe the local temperature and magnetic field in electrically biased VO2 devices, which are in agreement with the global transport measurement results. In pristine devices, the electrically-driven IMT proceeds through Joule heating up to the transition temperature while in ion-irradiated devices, the transition occurs non-thermally, well below the transition temperature. Our results provide the first direct evidence for non-thermal electrically induced IMT in a Mott insulator, highlighting the significant opportunities offered by NV quantum sensors in exploring nanoscale thermal and electrical behaviors in Mott materials.
Solsticial Hadley Cell Ascending Edge Theory from Supercriticality

How far the Hadley circulation's ascending branch extends into the summer hemisphere is a fundamental but incompletely understood characteristic of Earth's climate. Here, we present a predictive, analytical theory for this ascending edge latitude based on the extent of supercritical forcing. Supercriticality sets the minimum extent of a large-scale circulation based on the angular momentum and absolute vorticity distributions of the hypothetical state were the circulation absent. We explicitly simulate this latitude-by-latitude radiative-convective equilibrium (RCE) state. Its depth-averaged temperature profile is suitably captured by a simple analytical approximation that increases linearly with $\sin\varphi$, where $\varphi$ is latitude, from the winter to the summer pole. This, in turn, yields a one-third power-law scaling of the supercritical forcing extent with the thermal Rossby number. In moist and dry idealized GCM simulations under solsticial forcing performed with a wide range of planetary rotation rates, the ascending edge latitudes largely behave according to this scaling.
Significant Improvement in Planetary System Simulations from Statistical Averaging

Symplectic integrators are widely used for the study of planetary dynamics and other N-body problems. In a study of the outer solar system, we demonstrate that individual symplectic integrations can yield biased errors in the semimajor axes and possibly other orbital elements. The bias is resolved by studying an ensemble of initial conditions of the outer solar system. Such statistical sampling could significantly improve measurement of planetary system properties like their secular frequencies. We also compared the distributions of action-like variables between high and low accuracy integrations; traditional statistical metrics are unable to distinguish the distribution functions.
The Structure of Toxic Conversations on Twitter

Social media platforms promise to enable rich and vibrant conversations online; however, their potential is often hindered by antisocial behaviors. In this paper, we study the relationship between structure and toxicity in conversations on Twitter. We collect 1.18M conversations (58.5M tweets, 4.4M users) prompted by tweets that are posted by or mention major news outlets over one year and candidates who ran in the 2018 US midterm elections over four months. We analyze the conversations at the individual, dyad, and group level. At the individual level, we find that toxicity is spread across many low to moderately toxic users. At the dyad level, we observe that toxic replies are more likely to come from users who do not have any social connection nor share many common friends with the poster. At the group level, we find that toxic conversations tend to have larger, wider, and deeper reply trees, but sparser follow graphs. To test the predictive power of the conversational structure, we consider two prediction tasks. In the first prediction task, we demonstrate that the structural features can be used to predict whether the conversation will become toxic as early as the first ten replies. In the second prediction task, we show that the structural characteristics of the conversation are also predictive of whether the next reply posted by a specific user will be toxic or not. We observe that the structural and linguistic characteristics of the conversations are complementary in both prediction tasks. Our findings inform the design of healthier social media platforms and demonstrate that models based on the structural characteristics of conversations can be used to detect early signs of toxicity and potentially steer conversations in a less toxic direction.
Learning the Truth From Only One Side of the Story.

Learning under one-sided feedback (i.e., where examples arrive in an online fashion and the learner only sees the labels for examples it predicted positively on) is a fundamental problem in machine learning -- applications include lending and recommendation systems. Despite this, there has been surprisingly little progress made in ways to mitigate the effects of the sampling bias that arises. We focus on generalized linear models and show that without adjusting for this sampling bias, the model may converge sub-optimally or even fail to converge to the optimal solution. We propose an adaptive Upper Confidence Bound approach that comes with rigorous regret guarantees and we show that it outperforms several existing methods experimentally. Our method leverages uncertainty estimation techniques for generalized linear models to more efficiently explore uncertain areas than existing approaches which explore randomly.
Proximity Labeling at Non-Centrosomal Microtubule-Organizing Centers Reveals VAB-10B and WDR-62 as Distinct Microtubule Regulators

Microtubules are polarized intracellular polymers that play key roles in the cell including in transport, polarity, and cell division. Across eukaryotic cell types, microtubules adopt diverse intracellular organization to accommodate these distinct functions coordinated by specific cellular sites called microtubule organizing centers (MTOCs). Over 50 years of research on MTOC biology has focused mainly on the centrosome, however most differentiated cells employ non-centrosomal MTOCs (ncMTOCs) to organize their microtubules into diverse arrays which are critical to cell function. To identify essential ncMTOC components, we developed the biotin ligase-based proximity labeling approach TurboID for use in C. elegans. We identified proteins proximal to the microtubule minus end protein PTRN-1/Patronin at the apical ncMTOC of intestinal epithelial cells, focusing on two conserved proteins: spectraplakin protein VAB-10B and WDR-62, a protein we identify as homologous to vertebrate primary microcephaly disease gene WDR62. We found that WDR-62 and VAB-10B independently regulate the growth and localization of non-centrosomal microtubules and the apical targeting of microtubule minus end proteins. Depletion of VAB-10B resulted in disorganized microtubules and delayed localization of a microtubule nucleation complex γ-TuRC while loss of WDR-62 decreased the number of dynamic microtubules and abolished γ-TuRC localization. This regulation occurs downstream of cell polarity and in conjunction with actin. As this is the first report for non-centrosomal roles of WDR62 family proteins, our study expands the basic cell biological roles of this important disease protein. Together, our data suggest a division of labor where microtubule growth and anchoring are regulated by distinct complexes.
Generalized Stoichiometry and Biogeochemistry for Astrobiological Applications

A central need in the field of astrobiology is generalized perspectives on life that make it possible to differentiate abiotic and biotic chemical systems McKay (2008). A key component of many past and future astrobiological measurements is the elemental ratio of various samples. Classic work on Earth’s oceans has shown that life displays a striking regularity in the ratio of elements as originally characterized by Redfield (Redfield 1958; Geider and La Roche 2002; Eighty years of Redfield 2014). The body of work since the original observations has connected this ratio with basic ecological dynamics and cell physiology, while also documenting the range of elemental ratios found in a variety of environments. Several key questions remain in considering how to best apply this knowledge to astrobiological contexts: How can the observed variation of the elemental ratios be more formally systematized using basic biological physiology and ecological or environmental dynamics? How can these elemental ratios be generalized beyond the life that we have observed on our own planet? Here, we expand recently developed generalized physiological models (Kempes et al. 2012, 2016, 2017, 2019) to create a simple framework for predicting the variation of elemental ratios found in various environments. We then discuss further generalizing the physiology for astrobiological applications. Much of our theoretical treatment is designed for in situ measurements applicable to future planetary missions. We imagine scenarios where three measurements can be made—particle/cell sizes, particle/cell stoichiometry, and fluid or environmental stoichiometry—and develop our theory in connection with these often deployed measurements.
Synthesis, Characterization, and Nanodisc Formation of Non-ionic Polymers**

Although lipid nanodiscs are increasingly used in the structural studies of membrane proteins, drug delivery and other applications, the interaction between the nanodisc belt and the protein to be reconstituted is a major limitation. To overcome this limitation and to further broaden the scope of nanodiscs, a family of non-ionic amphiphilic polymers synthesized by hydrophobic functionalization of fructo-oligosaccharides/inulin is reported. We show the stability of lipid nanodiscs formed by these polymers against pH and divalent metal ions, and their magnetic-alignment properties. The reported results also demonstrate that the non-ionic polymers extract membrane proteins with unprecedented efficiency.
Temperature-mortality relationship in North Carolina, USA: Regional and urban-rural differences

Abstract Background Health disparities exist between urban and rural populations, yet research on rural-urban disparities in temperature-mortality relationships is limited. As inequality in the United States increases, understanding urban-rural and regional differences in the temperature-mortality association is crucial. Objective We examined regional and urban-rural differences of the temperature-mortality association in North Carolina (NC), USA, and investigated potential effect modifiers. Methods We applied time-series models allowing nonlinear temperature-mortality associations for 17 years (2000–2016) to generate heat and cold county-specific estimates. We used second-stage analysis to quantify the overall effects. We also explored potential effect modifiers (e.g. social associations, greenness) using stratified analysis. The analysis considered relative effects (comparing risks at 99th to 90th temperature percentiles based on county-specific temperature distributions for heat, and 1st to 10th percentiles for cold) and absolute effects (comparing risks at specific temperatures). Results We found null effects for heat-related mortality (relative effect: 1.001 (95% CI: 0.995–1.007)). Overall cold-mortality risk for relative effects was 1.019 (1.015–1.023). All three regions had statistically significant cold-related mortality risks for relative and absolute effects (relative effect: 1.019 (1.010–1.027) for Coastal Plains, 1.021 (1.015–1.027) for Piedmont, 1.014 (1.006–1.023) for Mountains). The heat mortality risk was not statistically significant, whereas the cold mortality risk was statistically significant, showing higher cold-mortality risks in urban areas than rural areas (relative effect for heat: 1.006 (0.997–1.016) for urban, 1.002 (0.988–1.017) for rural areas; relative effect for cold: 1.023 (1.017–1.030) for urban, 1.012 (1.001–1.023) for rural areas). Findings are suggestive of higher relative cold risks in counties with the less social association, higher population density, less green-space, higher PM2.5, lower education level, higher residential segregation, higher income inequality, and higher income (e.g., Ratio of Relative Risks 1.72 (0.68, 4.35) comparing low to high education). Conclusion Results indicate cold-mortality risks in NC, with potential differences by regional, urban-rural areas, and community characteristics.
Data Discovery Using Lossless Compression-Based Sparse Representation

Sparse representation has been widely used in data compression, signal and image denoising, dimensionality reduction and computer vision. While overcomplete dictionaries are required for sparse representation of multidimensional data, orthogonal bases represent one-dimensional data well. In this paper, we propose a data-driven sparse representation using orthonormal bases under the lossless compression constraint. We show that imposing such constraint under the Minimum Description Length (MDL) principle leads to a unique and optimal sparse representation for one-dimensional data, which results in discriminative features useful for data discovery.
Estimates of Certain Exit Probabilities for p -Adic Brownian Bridges

For each prime p, a diffusion constant together with a positive exponent specify a Vladimirov operator and an associated p-adic diffusion equation. The fundamental solution of this pseudo-differential equation gives rise to a measure on the Skorokhod space of p-adic valued paths that is concentrated on the paths originating at the origin. We calculate the first exit probabilities of paths from balls and estimate these probabilities for the Brownian bridges.
The Influence of Gait Stance and Vehicle Type On Pedestrian Kinematics and Injury Risk.

Pedestrians are one of the most vulnerable road users. In 2019, the USA reported the highest number of pedestrian fatalities number in nearly three decades. To better protect pedestrians in car-to-pedestrian collisions (CPC), pedestrian biomechanics must be better investigated. The pre-impact conditions of CPCs vary significantly in terms of the characteristics of vehicles (e.g., front-end geometry, stiffness, etc.) and pedestrians (e.g., anthropometry, posture, etc.). The influence of pedestrian gait posture has not been well analyzed. The purpose of this study was to numerically investigate the changes in pedestrian kinematics and injuries across various gait postures in two different vehicle impacts. Five finite element (FE) human body models, that represent the 50th percentile male in gait cycle, were developed and used to perform CPC simulations with two generic vehicle FE models representing a low-profile vehicle and a high-profile vehicle. In the impacts with the high-profile vehicle, a sport utility vehicle, the pedestrian models usually slide above the bonnet leading edge and report shorter wrap around distances than in the impacts with a low-profile vehicle, a family car/sedan (FCR). The pedestrian postures influenced the postimpact rotation of the pedestrian and consequently, the impacted head region. Pedestrian posture also influenced the risk of injuries in the lower and upper extremities. Higher bone bending moments were observed in the stance phase posture compared to the swing phase. The findings of this study should be taken into consideration when examining pedestrian protection protocols. In addition, the results of this study can be used to improve the design of active safety systems used to protect pedestrians in collisions.
The reward-complexity trade-off in schizophrenia

Action selection requires a policy that maps states of the world to a distribution over actions. The amount of memory needed to specify the policy (the policy complexity) increases with the state-dependence of the policy. If there is a capacity limit for policy complexity, then there will also be a trade-off between reward and complexity, since some reward will need to be sacrificed in order to satisfy the capacity constraint. This paper empirically characterizes the trade-off between reward and complexity for both schizophrenia patients and healthy controls. Schizophrenia patients adopt lower complexity policies on average, and these policies are more strongly biased away from the optimal reward-complexity trade-off curve compared to healthy controls. However, healthy controls are also biased away from the optimal trade-off curve, and both groups appear to lie on the same empirical trade-off curve. We explain these findings using a cost-sensitive actor-critic model. Our empirical and theoretical results shed new light on cognitive effort abnormalities in schizophrenia.
Unsupervised Learning of Visual 3D Keypoints for Control

Learning sensorimotor control policies from high-dimensional images crucially relies on the quality of the underlying visual representations. Prior works show that structured latent space such as visual keypoints often outperforms unstructured representations for robotic control. However, most of these representations, whether structured or unstructured are learned in a 2D space even though the control tasks are usually performed in a 3D environment. In this work, we propose a framework to learn such a 3D geometric structure directly from images in an end-to-end unsupervised manner. The input images are embedded into latent 3D keypoints via a differentiable encoder which is trained to optimize both a multi-view consistency loss and downstream task objective. These discovered 3D keypoints tend to meaningfully capture robot joints as well as object movements in a consistent manner across both time and 3D space. The proposed approach outperforms prior state-of-art methods across a variety of reinforcement learning benchmarks. Code and videos at this https URL
The Space Telescope Observatory

The Space Telescope is an international astronomical observatory which will be placed into a low earth orbit in December 1983. The observatory will provide astronomers the opportunity to use five different instruments (wide field/planetary camera, faint object camera, high-resolution spectrograph, faint-object spectrograph, and high speed photometer), and to do astrometry with the use of the fine guidance sensors used primarily for pointing control. These instruments, the spectral range available above the earth's atmosphere, and the spatial resolution available from the combination of a near-diffraction limited 94-in. primary mirror and the stability provided by the Pointing Control System provide a tremendous potential to the astronomical community.
Faster and Generalized Temporal Triangle Counting, via Degeneracy Ordering

Triangle counting is a fundamental technique in network analysis, that has received much attention in various input models. The vast majority of triangle counting algorithms are targeted to static graphs. Yet, many real-world graphs are directed and temporal, where edges come with timestamps. Temporal triangles yield much more information, since they account for both the graph topology and the timestamps. Temporal triangle counting has seen a few recent results, but there are varying definitions of temporal triangles. In all cases, temporal triangle patterns enforce constraints on the time interval between edges (in the triangle). We define a general notion (δ1,3, δ1,2, δ2,3)-temporal triangles that allows for separate time constraints for all pairs of edges. Our main result is a new algorithm, DOTTT (Degeneracy Oriented Temporal Triangle Totaler), that exactly counts all directed variants of (δ1,3, δ1,2, δ2,3)-temporal triangles. Using the classic idea of degeneracy ordering with careful combinatorial arguments, we can prove that DOTTT runs in O(mκlog m) time, where m is the number of (temporal) edges and κ is the graph degeneracy (max core number). Up to log factors, this matches the running time of the best static triangle counters. Moreover, this running time is better than existing. DOTTT has excellent practical behavior and runs twice as fast as existing state-of-the-art temporal triangle counters (and is also more general). For example, DOTTT computes all types of temporal queries in Bitcoin temporal network with half a billion edges in less than an hour on a commodity machine.