Technological Linkages, Market Structure, and Optimum Production Policies

There has been an increased interest in the efficacy of industrial policy. We show that policy design for vertically-related industries hinges on the nature of market interactions as well as technological linkages. Using a model in which final-good producers realize productivity gains from increasing domestic specialization of intermediate processes, we find no theoretical basis for presuming that an imperfectly competitive intermediates sector restricts output below the optimal level or that the market produces too many varieties. The direction of distortion depends on the relationship between the extent of the external economy and the market power of individual intermediates producers. Optimal corrective policies require two instruments: an output subsidy and a lump-sum tax or subsidy. If only one instrument is available, it may be optimal to tax instead of subsidize the externality-generating activity.

Invariant Measures for Dissipative Dynamical Systems: Abstract Results and Applications

In this work we study certain invariant measures that can be associated to the time averaged observation of a broad class of dissipative semigroups via the notion of a generalized Banach limit. Consider an arbitrary complete separable metric space $X$ which is acted on by any continuous semigroup $\{S(t)\}_{t \geq 0}$. Suppose that $\S(t)\}_{t \geq 0}$ possesses a global attractor $\mathcal{A}$. We show that, for any generalized Banach limit $\underset{T \rightarrow \infty}{\rm{LIM}}$ and any distribution of initial conditions $\mathfrak{m}_0$, that there exists an invariant probability measure $\mathfrak{m}$, whose support is contained in $\mathcal{A}$, such that $$\int_{X} \phi(x) d\mathfrak{m} (x) = \underset{T\to \infty}{\rm{LIM}} \frac{1}{T}\int_0^T \int_X \phi(S(t) x) d \mathfrak{m}_0(x) d t,$$ for all observables $\phi$ living in a suitable function space of continuous mappings on $X$. This work is based on a functional analytic framework simplifying and generalizing previous works in this direction. In particular our results rely on the novel use of a general but elementary topological observation, valid in any metric space, which concerns the growth of continuous functions in the neighborhood of compact sets. In the case when $\{S(t)\}_{t \geq 0}$ does not possess a compact absorbing set, this lemma allows us to sidestep the use of weak compactness arguments which require the imposition of cumbersome weak continuity conditions and limits the phase space $X$ to the case of a reflexive Banach space. Two examples of concrete dynamical systems where the semigroup is known to be non-compact are examined in detail.Comment: To appear in Communications in Mathematical Physic

Screening for Significant Behavior Problems in Diverse Young Children Living in Poverty

The development and use of first line screening instruments is an essential first step in assessing behavior disorders in very young children. The Early Childhood Behavior Screen (ECBS) is a parent-report measure for behavior disorders and is normed on young children (1–5 years old) living in poverty. The current study presents psychometric support for the discriminative validity of the ECBS’s 10-item Challenging Behavior Scale (CBS) as a first-line screener for externalizing behavior problems for preschool aged-children in poverty. The study’s sample included 673 participants (M age years = 2.81; 63.2 % male; 65.8 % African American) that all met the federal definitional standard for living in poverty. A confirmatory factor analysis was run to provide support for the ECBS factor structure. Receiver operating characteristics (ROC) curve analyses were used to test the CBS’s ability to distinguish between 428 clinic-referred children and 245 non-clinic-referred children. Results showed an acceptable fit model for the ECBS, providing further evidence of its construct validity. Optimal cut-scores by child age derived from the ROC curve analyses were provided with corresponding levels of sensitivity, specificity, and positive and negative predictive values. Sensitivity rates for cut scores ranged from 0.76 to 0.83 and specificity rates ranged from 0.88 to 0.95. Acceptable test–retest reliability and good internal consistency also was observed. The CBS quickly identifies young children from low-income, urban, diverse populations that may be at-risk for developing significant behavior disorders and should be considered by health care professionals who work with very young children

Consumer-Directed Prescription Drug Advertising: Effects on Public Health

This Paper will evaluate the effectiveness of the current FDA regulatory scheme regarding consumer-directed prescription drug advertising. Part II discusses the relevant history of consumer-directed prescription drug advertising of prescription drugs which is a relatively new practice in the United States. Possible explanations are reviewed for why the change in focus from physicians to consumers as the targets of such advertising has occurred. Part III explains the major classifications of consumer-directed advertising that the FDA has categorized and examines the differences existing among them. Part IV focuses on the current FDA regulatory scheme and begins to expose some of the difficulties of applying the current regulations to consumer-directed advertisements

Asymptotics of the Coleman-Gurtin model

This paper is concerned with the integrodifferential equation \partial_t u-\Delta u -\int_0^\infty \kappa(s)\Delta u(t-s)\,\d s + \varphi(u)=f arising in the Coleman-Gurtin's theory of heat conduction with hereditary memory, in presence of a nonlinearity $\varphi$ of critical growth. Rephrasing the equation within the history space framework, we prove the existence of global and exponential attractors of optimal regularity and finite fractal dimension for the related solution semigroup, acting both on the basic weak-energy space and on a more regular phase space.Comment: Accepted in Discrete and Continuous Dynamical Systems, Serie

Nanoscale assembly processes revealed in the nacroprismatic transition zone of Pinna nobilis mollusc shells

Intricate biomineralization processes in molluscs engineer hierarchical structures with meso-, nano-, and atomic architectures that give the final composite material exceptional mechanical strength and optical iridescence on the macroscale. This multiscale biological assembly inspires new synthetic routes to complex materials. Our investigation of the prism-nacre interface reveals nanoscale details governing the onset of nacre formation using high-resolution scanning transmission electron microscopy. A wedge polishing technique provides unprecedented, large-area specimens required to span the entire interface. Within this region, we find a transition from nanofibrillar aggregation to irregular early-nacre layers, to well-ordered mature nacre suggesting the assembly process is driven by aggregation of nanoparticles (~50-80 nm) within an organic matrix that arrange in fiber-like polycrystalline configurations. The particle number increases successively and, when critical packing is reached, they merge into early-nacre platelets. These results give new insights into nacre formation and particle-accretion mechanisms that may be common to many calcareous biominerals.Comment: 5 Figure