cssi/SciSciGPT-SciSciNet huggingface dataset:
Stochastic specification in random production models of cost-minimizing firms

Abstract We examine the implications of additive, homoskedastic errors for models of firm's cost-minimizing behavior. The premise is that some factors unobservable to the econometrician are known to the firm and must satisfy the theoretical restrictions imposed by cost minimization. We analyze additive homoskedastic errors for both the input demand model and the cost share model. We find that this simple error structure is inconsistent with rational behavior if some part of the stochastic component is known to the decision-maker. Input demand models violate nonnegativity and cannot represent homothetic technologies. For cost share systems, nonnegativity is also a potential problem but, surprisingly, concavity can be easily satisfied. An empirical application assesses the practical significance of these results.
Trade Models with Heterogeneous Firms: What About Importing?

Intermediate goods make up a large share of world trade. Yet trade models with heterogeneous firms focus almost exclusively on firms’ export decisions rather than their import decisions. We develop an analytically solvable model of a small open economy in which heterogeneous firms make endogenous import decisions. We view decisions about importing as decisions about technology adoption. In our model, firms weigh the benefit of operating a technology that uses imported intermediate goods against the fixed cost of developing trade relationships with foreign input suppliers. Similar to the selection effect in standard export-decision models, only the most efficient firms choose to import. In addition, the model features a technology upgrading effect, where importing improves a firm’s labor efficiency. The calibrated model quantifies the selection and technology upgrading effects, captures the large performance advantage associated with using imported intermediate goods, and generates large increases in trade from small decreases in tariffs.
Boron Concentrations in Milk from Mothers of Exclusively Breast-Fed Healthy Full-Term Infants Are Stable during the First Four Months of Lactation

Because boron is a bioactive element that satisfies several of the criteria for essentiality in humans, the aim of the present work was to determine the profile of boron metabolism in human milk during the first 4 mo of lactation. The concentration of boron and other minerals was determined in archived milk collected (1980-84) 1 time/mo for 4 mo from lactating mothers of full-term, exclusively breast-fed infants living in Houston, TX. A linear model (treating month as a continuous variable) indicated that B concentrations were stable (P = 0.14) between mo 1 [3.88 +/- 0.6 mumol (42 +/- 6.5 microg)/L milk] and 4 [3.24 +/- 0.6 micromol (35 +/- 6.5 microg)/L milk, mean +/- SEM]. Mg concentrations increased slightly over time (1.18 +/- 0.09 to 1.36 +/- 0.09 mmol/L, P < 0.0001), whereas Ca concentrations decreased slightly (7.01 +/- 0.29 to 6.68 +/- 0.29 mmol/L milk, P < 0.02) and Zn decreased substantially (0.04 +/- 0.004 to 0.02 +/- 0.004 mmol/L milk, P < 0.0001). Similarities in findings reported here and earlier (from samples collected in St. John's, Newfoundland) provide further evidence that boron may be metabolically regulated. Future investigations of boron regulatory mechanisms should focus on metabolism of bone as the major storage site of B and kidney excretion, the major excretory route for B.
Radio Polarization of the Young High-Magnetic-Field Pulsar PSR J1119-6127

We have investigated the radio polarization properties of PSR J1119� 6127, a recently discovered young radio pulsar with a large magnetic field. Using pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with the Australia Telescope Compact Array, we have determined a rotation measure for the pulsar of +842 � 23 rad m � 2 . These data, combined with archival polarimetry data taken at a center frequency of 1366 MHz with the Parkes telescope, were used to determine the polarization characteristics of PSR J1119� 6127 at both frequencies. The pulsar has a fractional linear polarization of � 75% and � 55% at 1366 and 2496 MHz, respectively, and the profile consists of a single, wide component. This pulse morphology and high degree of linear polarization are in agreement with previously noticed trends for young pulsars (e.g., PSR J1513� 5908). A rotating vector (RV) model fit of the position angle of linear polarization over pulse phase using the Parkes data suggests that the radio emission comes from the leading edge of a conal beam. We discuss PSR J1119� 6127 in the context of a recent theoretical model of pulsar spin-down, which can in principle be tested with polarization and timing data from this pulsar. Geometric constraints from the RV fit are currently insufficient to test this model with statistical significance, but additional data may allow such a test in the future. Subject headings: polarization — pulsars: individual (PSR J1119� 6127) — radio continuum: stars — stars: neutron Pulsar polarimetry is one of the keys to understanding the process and geometry of radio emission from pulsars. In the rotating vector (RV) model (Radhakrishnan & Cooke 1969) the polarization of pulsar radio emission is linked to the emission geometry in such a way that as the pulsar rotates, the axis of linear polarization is aligned with the projected direction on the sky of the pulsar’s magnetic dipole axis. The pulsar’s emission geometry itself may be described by two angles, each measured from the pulsar’s angular
Massive Degeneracy and Goldstone Bosons: A Challenge for the Light Cone

Wherein it is argued that the light front formalism has problems dealing with Goldstone symmetries. It is further argued that the notion that in hadron condensates can explain Goldstone phenomena is false. This talk can be summarized as follows: (1) Exact symmetries can be realized in Wigner or Goldstone mode. (2) When a symmetry is realized in Wigner mode the states of the theory form degenerate irreducible representations of the symmetry group and the lowest energy state is unique. (3) When a symmetry is realized in Goldstone mode the lowest energy state of the theory is infinitely degenerate, the states of the theory do not form irreducible representations of the symmetry group and there are massless particles coupled by the conserved currents to any one of the possible ground states. (4) In finite volume the signal of a Goldstone realization of a symmetry is that the number of nearly degenerate states grows rapidly with increasing volume and the gap between these states shrinks exponentially with the volume. (5) The existence of a condensate such as the magnetization, for a ferromagnet, or the staggered magnetization for an anti-ferromagnet, signals a Goldstone symmetry. This is because this condensate transforms non-trivially under themore » symmetry transformations and so its existence implies the ground state isn't unique. (6) PCAC means that the pion, kaon and eta are would be Goldstone bosons of the theory where the quark masses are set to zero. This interpretation is overwhelmingly supported by experimental data. This means that these particles are really the wiggling of the order parameter or condensate. (7) Finally, in order for the Goldstone particle to exist there has to be something to wiggle every place where the particle can exist. This means that the condensate that is the order parameter for this Goldstone symmetry cannot be confined to the interior of hadrons. Thus, to reiterate, the challenge for the Light Front is to show how the formalism gives rise to this sort of pattern of degeneracy when the physical volume of space becomes large.« less
Advances in 5-hydroxymethylfurfural production from biomass in biphasic solvents

Biomass derived 5-hydroxymethylfurfural (HMF) has emerged as an important platform chemical for the production of value added chemicals and liquid fuels that are currently obtained from petroleum. Although a significant amount of research has been performed over the past decade, the high production cost of HMF is still a bottleneck for its sustainable utilization for making other value added chemicals and fuels on a commercial scale. Among several factors, low product selectivity and high purification cost are major constraints. To address these drawbacks, HMF production methodology in recent years has been directed towards utilization of biphasic media for concurrent extraction of HMF into an organic phase immediately after its formation in the reactive phase. As a result, several dozens of journal and patent articles have appeared, demonstrating the benefit of biphasic media for effective HMF extraction. This review article summarizes the findings of the most recent research articles with critical discussion on the factors that enhance the performance of biphasic media. Particular emphasis has been given to the development of more effective extracting solvents and their beneficial effect in enhancing HMF yield and selectivity, improvement of partition coefficient, mechanistic role of the bi-functional acid catalysts and factors that control high HMF selectivity for solid catalysts.
ITERATIVELY SPECIFIED TREE-BASED REGRESSION: THEORY AND TRIP GENERATION EXAMPLE

Ordinary least-squares (OLS) regression is routinely applied by transportation analysts to forecast energy use, trip attractions, trip productions, automobile emissions, VMT growth, pavement condition, and accident occurrence to name a few examples. An important challenge when estimating OLS models is to derive an appropriate specification. Common misspecification errors include omission of important variables, inclusion of irrelevant variables, and inclusion of variables in an incorrect functional form. These errors often produce biased parameter estimates, inefficient parameter estimates, and an inability to conduct accurate hypothesis tests. Analysts typically rely on previous empirical research, a priori knowledge, and underlying theory to identify acceptable model functional forms, to determine important interactions, and to derive defensible models. In exploratory research, however, the analyst rarely knows a priori the correct form of the relationships being modeled, and previous research illuminating the “correct” relationships is scant. This paper presents an iterative modeling method that combines desirable properties of OLS with a heuristic procedure known as hierarchical tree-based regression (HTBR). This combined approach, named iteratively specified tree-based regression (ISTBR), is shown to provide insight into data structure provided by hierarchical tree-based regression, while retaining the desirable parametric properties of OLS. ISTBR equips the modeler with improved tools for exploring and identifying alternative model specifications and affords the analyst insight into systematic patterns or “structure” in data that might otherwise go undetected. An example of the ISTBR approach is provided using trip generation data from Michigan.
Pricing climate risk mitigation

Adaptation and geoengineering responses to climate change should be taken into account when estimating the social cost of carbon.
Synthesis of dopamine transporter selective 3-{2-(diarylmethoxyethylidene)}-8-alkylaryl-8-azabicyclo[3.2.1]octanes

Abstract A series of 3-{2-(diarylmethoxyethylidene)}-8-alkylaryl-8-azabicyclo[3.2.1]octanes was synthesized and the binding affinities of the compounds were determined at the dopamine and serotonin transporters. The 8-phenylpropyl analogues 8a ( K i =4.1 nM) and 8b ( K i =3.7 nM) were the most potent compounds of the series with binding affinities 3 times greater than GBR-12909. In addition, 8a (SERT/DAT=327) was over 300-fold more selective for the dopamine transporter than the serotonin transporter.
Cognitive and communicative abilities of Grey parrots

Abstract This paper presents results of almost 30 years of study of the cognitive and communicative activities of Grey parrots ( Psittacus erithacus ), conventionally regarded as mindless mimics. These studies have demonstrated that Grey parrots can solve various cognitive tasks and acquire and use English speech in ways that often resemble those of very young children. Examples include the concepts of same/different, colour, size and shape. The parrot Alex can also recognize and distinguish numbers up to six, and spontaneously demonstrated his ability to grasp the concept of "none". Given the evolutionary distance between birds and mammals, these results have intriguing implications for the evolution of intelligence, the study of comparative intelligence, and the care and maintenance of birds held in captivity in zoos and as companion animals.
Amino Acid Copolymers That Alleviate Experimental Autoimmune Encephalomyelitis In Vivo Interact with Heparan Sulfates and Glycoprotein 96 in APCs

Multiple sclerosis (MS) is an autoimmune disease that affects the CNS. One approved treatment for relapsing forms of MS is YEAK, a random copolymer of the amino acids tyrosine, glutamic acid, alanine, and lysine. YFAK, a second-generation copolymer composed of tyrosine, phenylalanine, alanine, and lysine, is more successful in treating experimental autoimmune encephalomyelitis, a mouse model of MS. Although originally designed and optimized based on the autoantigen myelin basic protein (MBP) and the MBP-derived peptide MBP85-99 presented to the MS-associated class II MHC molecule HLA-DR2, YEAK and YFAK also stimulate cytokine and chemokine production in APCs that lack class II MHC products. How YEAK and YFAK copolymers interact with APCs remains enigmatic. We used biotinylated YFAK to affinity-purify YFAK-interacting proteins from RAW264.7 cells and tested APCs from mice deficient in several of the newly identified interactors for their capacity to secrete CCL22 in response to YEAK and YFAK. We propose that initial contact of YFAK with cells is mediated mainly by electrostatic interactions, and find that interaction of YFAK with host proteins is strongly dependent on ionic strength. Cells deficient in enzymes involved in sulfation of proteins and proteoglycans showed strongly reduced binding of biotinylated YFAK. Lastly, cells stimulated with YFAK in the presence of heparin, structurally similar to heparan sulfates, failed to produce CCL22. We conclude that charge-dependent interactions of copolymers that alleviate MS/experimental autoimmune encephalomyelitis are critical for their effects exerted on APCs and may well be the main initial mediators of these therapeutically active copolymers.
DDP: a tool for life-cycle risk management

At JPL we have developed and implemented a process for achieving life-cycle risk management. This process has been embodied in a software tool and is called defect detection and prevention (DDP). The DDP process can be succinctly stated as: determine where we want to be, what could get in the way and how we will get there. The "determine where we want to be" is captured as trees of requirements and the "what could get in the way" is captured as trees of potential failure modes. Scoring the impacts of these failure modes on the requirements results in a prioritized set of failure modes. The user then selects from a set of preventative measures, analyses, process controls and tests (PACTs) each of which has an effectiveness versus the various failure modes. It is the goal of the DDP process to optimally select the subset of the PACTs which minimizes the residual risk subject to the project resource constraints. The DDP process is intended to facilitate risk management over the entire project life cycle beginning with architectural and advanced technology decisions all the way through operation. As the project design, technology content, and implementation approach matures, the requirements and failure mode trees are elaborated upon to accommodate the additional information. Thus, the DDP process is a systematic, continuous, top-down approach to managing risk. Implementation of the DDP process requires a critical mass of expertise (usually the project team and a few specialists) and captures both their engineering judgement as well as available quantitative data. This additional data may result from models, layouts, prototype testing, other focused risk evaluations and institutional experiences. The DDP process also identifies areas where additional information would be advantageous, thus allowing a project to target critical areas of risk or risk uncertainty. This also allows the project to identify those areas which would benefit the most from application of other quantitative tools and methods (e.g. Monte Carlo simulations, FMECAs, fault trees). The software tool supports the DDP process by providing guidance for implementing the process steps, graphical visualizations of the various trees, their interrelationships and the current risk landscape. The tool is capable of supporting on-the-fly knowledge elicitation as well as integrating off-line deliberations. There are a variety of available outputs including graphs, trees and reports as well as clear identification of the driving requirements, "tall-pole" residual risks and the PACTs which have been selected and agreed upon. The DDP process has been applied at various levels of assembly including the system and subsystem levels, as well as down to the component level. Recently, significant benefits have been realized from application to advanced technologies, where the focus has been on increasing the infusion rates of these technologies by identification and mitigation of risks prior to delivery to a project
Single-Scale Natural SUSY

We consider the prospects for natural SUSY models consistent with current data. Recent constraints make the standard paradigm unnatural so we consider what could be a minimal extension consistent with what we now know. The most promising such scenarios extend the MSSM with new tree-level Higgs interactions that can lift its mass to at least 125 GeV and also allow for flavor-dependent soft terms so that the third generation squarks are lighter than current bounds on the first and second generation squarks. We argue that a common feature of almost all such models is the need for a new scale near 10 TeV, such as a scale of Higgsing or confinement of a new gauge group. We consider the question whether such a model can naturally derive from a single mass scale associated with supersymmetry breaking. Most such models simply postulate new scales, leaving their proximity to the scale of MSSM soft terms a mystery. This coincidence problem may be thought of as a mild tuning, analogous to the usual problem. We find that a single mass scale origin is challenging, but suggest that a more natural origin for such a new dynamical scale is the gravitino mass, m3=2, in theories where the MSSM soft terms are a loop factor below m3=2. As an example, we build a variant of the NMSSM where the singlet S is composite, and the strong dynamics leading to compositeness is triggered by masses of order m3=2 for some fields. Our focus is the Higgs sector, but our model is compatible with a light stop (either with the first and second generation squarks heavy, or with R-parity violation or another mechanism to hide them from current searches). All the interesting low-energy mass scales, including linear terms for S playing a key role in EWSB, arise dynamically from the single scale m3=2. However, numerical coefficients from RG effects and wavefunction factors in an extra dimension complicate the otherwise simple story.
Profiting from empowerment? Investigating dissemination avenues for educational technology content within an emerging market solutions project

The Stills in Sync (SIS) project is a joint initiative of the non­profit organization PlanetRead and the global information and communication technology (ICT) company Hewlett Packard (HP). The SIS project entails creating a multi­media product designed to enhance literacy in rural India through the revival of regional folksongs on relevant social issues. This product utilizes the Same Language Subtitling (SLS) feature that won the World Bank Development Marketplace Award in 2002 and the Tech Laureate in education honor from the Technology Museum of Innovation (San Jose) in 2003. This paper explores the dissemination avenues of the SLS folksongs product and its effects within the Inclusive Community (i­community) of HP in Kuppam, India. This community has functioned as a social and economic laboratory in which HP tested new technologies. Analyzing this test environment makes apparent the dichotomy between corporate responsibility and community development. Keeping the balance between profitable goals of the ICT business and development goals towards sustainable social and economic reforms has been illustrated by the survey results in this paper.
Employment and Economic Well-Being of People With and Without Disabilities Before and After the Great Recession

The latest U.S. economic recession, commonly referred to as the Great Recession, has had a far-reaching impact, but its effects may be disproportionately experienced by working-age people with disa...
Cooling Rates for Relativistic Electrons Undergoing Compton Scattering in Strong Magnetic Fields

For inner magnetospheric models of hard X-ray and gamma-ray emission in high-field pulsars and magnetars, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. This is in part due to the proximity of a hot soft photon bath from the stellar surface to putative radiation dissipation regions in the inner magnetosphere. Moreover, because the scattering process becomes resonant at the cyclotron frequency, the effective cross section exceeds the classical Thomson value by over two orders of magnitude, thereby enhancing the efficiency of continuum production and the cooling of relativistic electrons. This paper presents computations of the electron cooling rates for this process, which are needed for resonant Compton models of non-thermal radiation from such highly magnetized pulsars. The computed rates extend previous calculations of magnetic Thomson cooling to the domain of relativistic quantum effects, sampled near and above the quantum critical magnetic field of 44.13 TG. This is the first exposition of fully relativistic, quantum magnetic Compton cooling rates for electrons, and it employs both the traditional Johnson & Lippmann cross section and a newer Sokolov & Ternov (ST) formulation of Compton scattering in strong magnetic fields. Such ST formalism is formally correct for treating spin-dependent effects that are important in the cyclotron resonance and has not been addressed before in the context of cooling by Compton scattering. The QED effects are observed to profoundly lower the rates below extrapolations of the familiar magnetic Thomson results, as expected, when recoil and Klein-Nishina reductions become important.
A threshold phenomenon for random independent sets in the discrete hypercube

Let I be an independent set drawn from the discrete d-dimensional hypercube Qd = {0, 1}d according to the hard-core distribution with parameter λ > 0 (that is, the distribution in which each independent set I is chosen with probability proportional to λ|I|). We show a sharp transition around λ = 1 in the appearance of I: for λ > 1, min{|I ∩ Ɛ|, |I ∩ |} = 0 asymptotically almost surely, where Ɛ and are the bipartition classes of Qd, whereas for λ |} is asymptotically almost surely exponential in d. The transition occurs in an interval whose length is of order 1/d. A key step in the proof is an estimation of Zλ(Qd), the sum over independent sets in Qd with each set I given weight λ|I| (a.k.a. the hard-core partition function). We obtain the asymptotics of Zλ(Qd) for $\gl>\sqrt{2}-1$ , and nearly matching upper and lower bounds for $\gl \leq \sqrt{2}-1$ , extending work of Korshunov and Sapozhenko. These bounds allow us to read off some very specific information about the structure of an independent set drawn according to the hard-core distribution. We also derive a long-range influence result. For all fixed λ > 0, if I is chosen from the independent sets of Qd according to the hard-core distribution with parameter λ, conditioned on a particular v ∈ Ɛ being in I, then the probability that another vertex w is in I is o(1) for w ∈ but Ω(1) for w ∈ Ɛ.
Clinical significance of bone changes in osteoarthritis

Knee OA is thought to be a largely mechanically-driven disease. Pertinent to this, bone is a dynamic tissue that adapts to loads by remodeling to meet its mechanical demands (Wolff's Law) [1,2]. As such, it is not surprising that bone changes, such as increased tibial plateau area and bone turnover, occur early in OA [3,4]. Recently, MRI-based 3D bone shape has been shown to track concurrently with OA onset, and to predict incidence of radiographic knee OA 12 months before its onset [5]. Further, in radiographically normal tibiofemoral knee joints, subchondral bone changes, such as bone marrow lesions (BMLs) on MRIs, are common. Although MRIs allow direct visualization and morphologic evaluation of joint tissues not otherwise discernible on x-ray, their specific pathologies need to be examined by direct evaluation to gain further pathophysiologic insight. BMLs adjacent to the subchondral plate have been shown to have increased bone volume fraction and increased trabecular thickness, but reduced tissue mineral density (i.e., hypomineralized) [6], consistent with OA being associated with increased bone turnover. BMLs may render these areas mechanically compromised and susceptible to attrition. Indeed, BMLs are strongly associated with occurrence of subchondral bone attrition (SBA) [7]. Both subchondral bone abnormalities are associated with cartilage loss as well [8,9]. In keeping with knee OA being mechanically-driven, meniscal pathology, often the result of injury, is associated with new and enlarging BMLs [10]. Further, malalignment is associated with both BMLs and SBA [11,12]. The contributions of these structural abnormalities to the clinical manifestations of knee OA are becoming better understood. While it is widely thought that there is a structure-symptom discordance in knee OA, such observations do not take into account all of the potential factors that can contribute to between-person differences in the pain experience [13]. Recent work that used novel methodology to overcome this problem has demonstrated that pain fluctuation is associated with changes in BMLs, as well as synovitis and effusion [14]. SBA has also been associated with knee pain [15], but the relationship of osteophytes to pain has been conflicting. A challenge that remains in studying the specific contribution of pathologic features of OA to pain is the co-existence of multiple MRI abnormalities, making it difficult to identify individual pathologic features' effects. Understanding the pathophysiologic sequences and consequences of OA pathology will guide rational therapeutic targeting. Importantly, rational treatment targets also require understanding what particular structures contribute to pain as pain is the reason patients seek medical care.
Analyzing Regional Inequality in Post-Mao China in a GIS Environment

Regional inequality in China has attracted considerable scholarly attention, but the use of geographic information system (GIS) techniques for rigorous analysis remains limited. This paper utilizes recent data and GIS and spatial statistical techniques to analyze changing patterns of regional inequality in China from 1978 to 2000. It also identifies the changing clusters of regional development in China. We illustrate that regional inequality in China is sensitive to development trajectories of the provinces, and that conventional measures of regional inequality mask geographical clustering. Patterns of change are explained by both contextual and regression analyses. Journal of Economic Literature, Classification Numbers: F21, G32, P31. 16 figures, 3 tables, 30 references.
Reaction kinetics in polymer melts

We study the reaction kinetics of end-functionalized polymer chains dispersed in an unreactive polymer melt. Starting from an infinite hierarchy of coupled equations for many-chain correlation functions, a closed equation is derived for the 2nd order rate constant k after postulating simple physical bounds. Our results generalize previous 2-chain treatments (valid in dilute reactants limit) by Doi [#!doi:inter2!#], de Gennes [#!gennes:polreactionsiandii!#], and Friedman and O'Shaughnessy [#!ben:interdil_all_aip!#], to arbitrary initial reactive group density n0 and local chemical reactivity Q. Simple mean field (MF) kinetics apply at short times, \(\).For high Q, a transition occurs to diffusion-controlled (DC) kinetics with \(\) (where xt is rms monomer displacement in time t) leading to a density decay \(\). If n0 exceeds the chain overlap threshold, this behavior is followed by a regime where \(\) during which k has the same power law dependence in time, \(\), but possibly different numerical coefficient. For unentangled melts this gives \(\) while for entangled cases one or more of the successive regimes \(\),t-3/8 and t-3/4 may be realized depending on the magnitudes of Q and n0. Kinetics at times longer than the longest polymer relaxation time \(\) are always MF. If a DC regime has developed before \(\) then the long time rate constant is \(\) where R is the coil radius. We propose measuring the above kinetics in a model experiment where radical end groups are generated by photolysis.
A low-power 170-MHz discrete-time analog FIR filter

A 170-MHz analog finite impulse response (FIR) filter operating from a single 3.3-V supply is described. The design has been fabricated in the HP 1.2-/spl mu/m CMOS process and has an area of 2.35 mm by 1.97 mm including bonding pads. This 9-tap filter dissipates 70 mW when operating at 170 MHz. The multipliers are implemented using multiplying digital-to-analog converters (MDAC's) with 6-b resolution.
Asymptotic growth of cumulative and regenerative beam break-up instabilities in linear accelerators

With the use of a simple model, it is shown that the asymptotic growth of the cumulative beam break-up instability is independent of the linear transverse focusing. The analysis is extended to include the transition from the cumulative to the regenerative type, both in the presence and absence of a focusing magnetic field. >
An Analytical Investigation of Current-Injected Control for Constant-Frequency Switching Regulators

State-space averaging and linearization are applied to current-injected, constant-frequency switching regulators, resulting in a generalized two-loop system representation. The boost regulator is examined in detail to show that, as a theoretical goal, wide-bandwidth, first-order behavior can be achieved with no right-half-plane zeroes. Actual performance may be limited by switching frequency interference considerations.
Are rules and boundaries sufficient to limit harmful central bank discretion? Lessons from Europe

Abstract Marvin Goodfriend׳s (2014) insightful, informative and provocative work explains concisely and convincingly why the Fed needs rules and boundaries. This paper reviews the broader institutional design problem regarding the effectiveness of the central bank in practice and confirms the need for rules and boundaries. The framework proposed for improving the Fed incorporates key elements that have already been adopted in the European Union. The case of ELA provision by the ECB and the Central Bank of Cyprus to Marfin-Laiki Bank during the crisis, however, suggests that the existence of rules and boundaries may not be enough to limit harmful discretion. During a crisis, novel interpretations of the legal authority of the central bank may be introduced to create a grey area that might be exploited to justify harmful discretionary decisions even in the presence of rules and boundaries. This raises the question how to ensure that rules and boundaries are respected in practice.
A rail-transit people-mover headway comparison

For many years, General Railway Signal Company has supplied control systems for conventional rail transit. Headways for these systems range from minutes or hours down to as low as 75 s. In the last few years, the company has supplied control systems for people-mover applications in which minimum headways of 10-20 s have been achieved. There are many factors working together to permit achievement of this large reduction in headway. These factors are identified and evaluated for their impact on capacity. The fundamentals underlying the disparity in headway are discussed from the viewpoint of potential for increased capacity of rail transit.
Principles of microRNA regulation of a human cellular signaling network

MicroRNAs (miRNAs) are endogenous ∼22-nucleotide RNAs, which suppress gene expression by selectively binding to the 3′-noncoding region of specific messenger RNAs through base-pairing. Given the diversity and abundance of miRNA targets, miRNAs appear to functionally interact with various components of many cellular networks. By analyzing the interactions between miRNAs and a human cellular signaling network, we found that miRNAs predominantly target positive regulatory motifs, highly connected scaffolds and most downstream network components such as signaling transcription factors, but less frequently target negative regulatory motifs, common components of basic cellular machines and most upstream network components such as ligands. In addition, when an adaptor has potential to recruit more downstream components, these components are more frequently targeted by miRNAs. This work uncovers the principles of miRNA regulation of signal transduction networks and implies a potential function of miRNAs for facilitating robust transitions of cellular response to extracellular signals and maintaining cellular homeostasis.
Phoenix Miracles in Emerging Markets: Recovering without Credit from Systemic Financial Crises

ABSTRACT Using a sample of emerging markets that are integrated into global bond markets, we analyze thecollapse and recovery phase of output collapses that coincide with systemic sudden stops, definedas periods of skyrocketing aggregate bond spreads and large capital flow reversals. Our findingsindicate the presence of a very similar pattern across different episodes: output recovers withvirtually no recovery in either domestic or foreign credit, a phenomenon that we call PhoenixMiracle, where output “rises from its ashes”, suggesting that firms go through a process of financialengineering to restore liquidity outside the formal credit markets. Moreover, we show that the USGreat Depression could be catalogued as a Phoenix Miracle. However, in contrast to the US GreatDepression, EM output collapses occur in a context of accelerating price inflation and falling realwages, casting doubts on price deflation and nominal wage rigidity as key elements in explainingoutput collapse, and suggesting that financial factors are prominent for understanding thesecollapses.Guillermo A. CalvoInter-American Development Bank1300 New York Ave., N.W.Washington, DC 20577and NBERgcalvo@iadb.orgAlejandro IzquierdoInter-American Development Bank1300 New York Ave., N.W.Washington, DC 20577alejandroi@iadb.orgErnesto TalviCERESAntonio Costa 347611300 MontevideoUruguayetalvi@ceres-uy.org
Quantum hall fluids

We review the effective field theory treatment of topological quantum fluids, focussing on the Hall fluids.
Too big to fail? The puzzling darkness of massive Milky Way subhaloes

ABSTRACT We show that dissipationless CDM simulations predict that the majority of themost massive subhalos of the Milky Way are too dense to host any of its brightsatellites (L V > 10 5 L ). These dark subhalos have circular velocities at infall ofV infall = 30 1070kms 1 and infall masses of [0:2 4] 10 M . Unless the Milky Way isa statistical anomaly, this implies that galaxy formation becomes e ectively stochasticat these masses. This is in marked contrast to the well-established monotonic relationbetween galaxy luminosity and halo circular velocity (or halo mass) for more massivehalos. We show that at least two (and typically four) of these massive dark subhalosare expected to produce a larger dark matter annihilation ux than Draco. It maybe possible to circumvent these conclusions if baryonic feedback in dwarf satellites ordi erent dark matter physics can reduce the central densities of massive subhalos byorder unity on a scale of 0.3 { 1 kpc.Key words: Galaxy: halo { galaxies: abundances { dark matter { cosmology: theory
Spatiotemporal dynamics of pacing in models of anatomical reentry

Reentry around non-conducting ventricular scar tissue, which often causes lethal arrhythmias, is typically treated by rapid stimulation from an implantable defibrillator. However, the mechanisms of termination (success and failure) are poorly understood. To elucidate such mechanisms, we studied pacing of anatomical reentry in 1-D and 2-D excitable cardiac media models. Our results suggest that the existence of inhomogeneity in the reentry circuit is essential for pacing termination of tachycardia to be successful. Considering the role of such inhomogeneities may lead to more effective pacing algorithms.
Learning to make predictions in partially observable environments without a generative model

When faced with the problem of learning a model of a high-dimensional environment, a common approach is to limit the model to make only a restricted set of predictions, thereby simplifying the learning problem. These partial models may be directly useful for making decisions or may be combined together to form a more complete, structured model. However, in partially observable (non-Markov) environments, standard model-learning methods learn generative models, i.e. models that provide a probability distribution over all possible futures (such as POMDPs). It is not straightforward to restrict such models to make only certain predictions, and doing so does not always simplify the learning problem. In this paper we present prediction profile models: non-generative partial models for partially observable systems that make only a given set of predictions, and are therefore far simpler than generative models in some cases. We formalize the problem of learning a prediction profile model as a transformation of the original model-learning problem, and show empirically that one can learn prediction profile models that make a small set of important predictions even in systems that are too complex for standard generative models.
Does Every Contractive Analytic Function in a Polydisk have a Dissipative n-Dimensional Scattering Realization?

The answer to the title question is “no.” The Kaijser–Varopoulos counterexample to the three-variable von Neumann inequality shows that conservative realizations do not always exist; in this note we show that this same example can be used to prove that dissipative realizations need not exist. (This is a consequence of the particular features of this example; it need not be true of every counterexample to von Neumann’s inequality.)
Importance of the medial meniscus in the anterior cruciate ligament‐deficient knee

The incidence of meniscal tears in the chronically anterior cruciate ligament-deficient knee is increased, particularly in the medial meniscus because it performs an important function in limiting knee motion. We evaluated the role of the medial meniscus in stabilizing the anterior cruciate ligament-deficient knee and hypothesized that the resultant force in the meniscus is significantly elevated in the anterior cruciate ligament-deficient knee. To test this hypothesis, we employed a robotic/universal force-moment sensor testing system to determine the increase in the resultant force in the human medial meniscus in response to an anterior tibial load following transection of the anterior cruciate ligament. We also measured changes in the kinematics of the knee in multiple degrees of freedom following medial meniscectomy in the anterior cruciate ligament-deficient knee. In response to a 134-N anterior tibial load, the resultant force in the medial meniscus of the anterior cruciate ligament-deficient knee increased significantly compared with that in the meniscus of the intact knee; it increased by a minimum of 10.1 N (52%) at full knee extension to a maximum of 50.2 N (197%) at 60 degrees of flexion. Medial meniscectomy in the anterior cruciate ligament-deficient knee also caused a significant increase in anterior tibial translation in response to the anterior tibial load, ranging from an increase of 2.2 mm at full knee extension to 5.8 mm at 60 degrees of flexion. Conversely, coupled internal tibial rotation in response to the load decreased significantly, ranging from a decrease of 2.5 degrees at 15 degrees of knee flexion to 4.7 degrees at 60 degrees of flexion. Our data confirm the hypothesis that the resultant force in the medial meniscus is significantly greater in the anterior cruciate ligament-deficient knee than in the intact knee when the knee is subjected to anterior tibial loads. This indicates that the demand on the medial meniscus in resisting anterior tibial loads is increased in the anterior cruciate ligament-deficient knee compared with in the intact knee, suggesting a mechanism for the increased incidence of medial meniscal tears observed in chronically anterior cruciate ligament-deficient patients. The large changes in kinematics due to medial meniscectomy in the anterior cruciate ligament-deficient knee confirm the important role of the medial meniscus in controlling knee stability. These findings suggest that the reduction of resultant force in the meniscus may be a further motive for reconstructing the anterior cruciate ligament, with the goal of preserving meniscal integrity.
ON THE EVOLUTION OF DIFFERENTIATED MULTICELLULARITY

Most conspicuous organisms are multicellular and most multicellular organisms develop somatic cells to perform specific, nonreproductive tasks. The ubiquity of this division of labor suggests that it is highly advantageous. In this article I present a model to study the evolution of specialized cells. The model allows for unicellular and multicellular organisms that may contain somatic (terminally differentiated) cells. Cells contribute additively to a quantitative trait. The fitness of the organism depends on this quantitative trait (via a benefit function), the size of the organism, and the number of somatic cells. The model allows one to determine when somatic cells are advantageous and to calculate the optimum number (or fraction) of reproductive cells. I show that the fraction of reproductive cells is always surprisingly high. If somatic cells are very small, they can outnumber reproductive cells but their biomass is still less than the biomass of reproductive cells. I discuss the biology of primitive multicellular organisms with respect to the model predictions. I find a good agreement and outline how this work can be used to guide further quantitative studies of multicellularity.
The robustness of identified VAR conclusions about money

Abstract This paper presents a new way to assess robustness of claims from identified VAR work. All possible identifications are checked for the one that is worst for the claim, subject to the restriction that the VAR produce reasonable impulse responses to shocks. The parameter on which the claim is based need not be identified; thus, one can assess claims in large models using minimal restrictions. The technique reveals only weak support for the claim that monetary policy shocks contribute a small portion of the forecast error variance of post-war U.S. output in standard 6-variable and 13-variable models.
A multivariable extension of the Tsypkin criterion using a Lyapunov-function approach

For analyzing the stability of discrete-time systems containing a feedback nonlinearity, the Tsypkin criterion is the closest analog to the Popov criterion which is used for analyzing such systems in continuous time. Traditionally, the proof of this criterion is based upon input-output properties and function analytic methods. In this paper we extend the Tsypkin criterion to multivariable systems containing an arbitrary number of monotonic sector-bounded memoryless time-invariant nonlinearities, along with providing a Lyapunov function proof for this classical result.
Chemistry of electron-rich conjugated polyenes V. Regio- and stereo-selectivity in Diels-Alder reactions of 1-alkoxy-1,3-butadienes and β-cyanostyrenes†

Effects of substituents in diene and dienophile on the regio- and stereo-selectivity of Diels-Alder reactions have been studied on cycloadditions of alkoxy-substituted 1,3-butadienes (1) and 2-substituted cyanoethenes (2). The regioselectivity is always very high, and is determined by the magnitude of the orbital coefficients of the interacting carbon atoms according to the frontier orbital theory. The stereoselectivity is more determined by steric factors than by secondary orbital overlap. The results point to a transition state, in which the planes of diene and dienophile, are non-parallel (Figure 1).
Classification of almost quarter-pinched manifolds

We show that if a simply connected manifold is almost quarter-pinched, then it is diffeomorphic to a CROSS or a sphere.
Demand Analysis Using Strategic Reports: An Application to a School Choice Mechanism

Several school districts use assignment systems that give students an incentive to misrepresent their preferences. We find evidence consistent with strategic behavior in Cambridge. Such strategizing can complicate preference analysis. This paper develops empirical methods for studying random utility models in a new and large class of school choice mechanisms. We show that preferences are non-parametrically identified under either sufficient variation in choice environments or a preference shifter. We then develop a tractable estimation procedure and apply it to Cambridge. Estimates suggest that while 82% of students are assigned to their stated first choice, only 72% are assigned to their true first choice because students avoid ranking competitive schools. Assuming that students behave optimally, the Immediate Acceptance mechanism is preferred by the average student to the Deferred Acceptance mechanism by an equivalent of 0.08 miles. The estimated difference is smaller if beliefs are biased, and reversed if students report truthfully.
Does Global Liquidity Matter for Monetary Policy in the Euro Area

Global excess liquidity prevalent across the world's financial markets (or its sudden absence) is sometimes believed to limit sovereign monetary policy even in large economies such as the euro area. However, there is still discussion about what constitutes global excess liquidity and how exactly it shapes the policy environment. Our approach adjusts liquidity for a longer-term interest rate and output effects and focuses on US and Japanese liquidity as relevant proxies for global developments from a euro area perspective. We find that, in particular, excess liquidity in the US tends to lead developments in euro area liquidity. US excess liquidity is also consistently positive as a determinant of euro area inflation and is shown to be Granger-causal for euro area inflation in an out-of-sample forecasting exercise. There is some evidence that, at least in part, this result seems to be related to a weakening of the effectiveness of monetary policy in the euro area interest during times of excessive US liquidity. In contrast, the influence of euro area excess liquidity on euro area inflation is more limited.
PRICE TRANSMISSION AND ASYMMETRIC ADJUSTMENT IN THE SPANISH DAIRY SECTOR

Asymmetric threshold vector error correction models are applied to monthly price data to analyse price relationships and patterns of transmission among farm and retail markets for a variety of dairy products in Spain. The results suggest that asymmetries affect a conspicuous part of the raw milk processed in Spain. Implications for the organizational structure of Spanish dairy markets are offered.