The hormones of invertebrates

Thesis (M.A.)--Boston University, 193

Structure and Dynamics of the Quasi-Liquid Layer at the Surface of Ice from Molecular Simulations

We characterized the structural and dynamical properties of the quasi-liquid layer (QLL) at the surface of ice by molecular dynamics simulations with a thermodynamically consistent water model. Our simulations show that for three low-index ice surfaces only the outermost molecular layer presents short-range and mid-range disorder and is diffusive. The onset temperature for normal diffusion is much higher than the glass temperature of supercooled water, although the diffusivity of the QLL is higher than that of bulk water at the corresponding temperature. The underlying subsurface layers impose an ordered template, which produces a regular patterning of the ice/water interface at any temperature, and is responsible for the major differences between QLL and bulk water, especially for what concern the dynamics and the mid-range structure of the hydrogen-bonded network. Our work highlights the need of a holistic approach to the characterization of QLL, as a single experimental technique may probe only one specific feature, missing part of the complexity of this fascinating system.Comment: 6 Figure

The institutional character of computerized information systems

We examine how important social and technical choices become part of the history of a computer-based information system (CB/SJ and embedded in the social structure which supports its development and use. These elements of a CBIS can be organized in specific ways to enhance its usability and performance. Paradoxically, they can also constrain future implementations and post-implementations.We argue that CBIS developed from complex, interdependent social and technical choices should be conceptualized in terms of their institutional characteristics, as well as their information-processing characteristics. The social system which supports the development and operation of a CBIS is one major element whose institutional characteristics can effectively support routine activities while impeding substantial innovation. Characterizing CBIS as institutions is important for several reasons: (1) the usability of CBIS is more critical than the abstract information-processing capabilities of the underlying technology; (2) CBIS that are well-used and have stable social structures are more difficult to replace than those with less developed social structures and fewer participants; (3) CBIS vary from one social setting to another according to the ways in which they are organized and embedded in organized social systems. These ideas are illustrated with the case study of a failed attempt to convert a complex inventory control system in a medium-sized manufacturing firm

Inelastic Dark Matter at the LHC Lifetime Frontier: ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA

Visible signals from the decays of light long-lived hidden sector particles have been extensively searched for at beam dump, fixed-target, and collider experiments. If such hidden sectors couple to the Standard Model through mediators heavier than $\sim 10$ GeV, their production at low-energy accelerators is kinematically suppressed, leaving open significant pockets of viable parameter space. We investigate this scenario in models of inelastic dark matter, which give rise to visible signals at various existing and proposed LHC experiments, such as ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA. These experiments can leverage the large center of mass energy of the LHC to produce GeV-scale dark matter from the decays of dark photons in the cosmologically motivated mass range of $\sim 1-100$ GeV. We also provide a detailed calculation of the radiative dark matter-nucleon/electron elastic scattering cross section, which is relevant for estimating rates at direct detection experiments.Comment: 21 pages, 9 figure

Heavy Neutral Leptons at FASER

We study the prospects for discovering heavy neutral leptons at ForwArd Search ExpeRiment (FASER), the newly proposed detector at the LHC. Previous studies showed that a relatively small detector with ~10 m length and ~1 m cross sectional area can probe large unconstrained parts of parameter space for dark photons and dark Higgs bosons. In this work we show that FASER will also be sensitive to heavy neutral leptons that have mixing angles with the active neutrinos that are up to an order of magnitude lower than current bounds. In particular, this is true for heavy neutral leptons produced dominantly in $B$-meson decays, in which case FASER's discovery potential is comparable to the proposed SHiP detector. We also illustrate how the search for heavy neutral leptons at FASER will be complementary to ongoing searches in high-$p_T$ experiments at the LHC and can shed light on the nature of dark matter and the process of baryogenesis in the early Universe.Comment: 24 pages, 9 figures; matches to the published versio

Methodological Frontiers of Public Finance Field Experiments

The purpose of this article is to demonstrate how a rich array of methods can be applied to increase the relevance of field experiments in public economics. Two cross-cutting themes are important in multiple phases of the research. First, greater statistical sophistication can draw more value from a field experiment without obscuring the simple and compelling information from the differences in average outcomes of intervention and control groups. Second, the methodological frontier is interdisciplinary, drawing on knowledge and techniques developed in psychology, anthropology, and sociology that can be adapted in order to make public finance field experiments more useful.

Does the Doctor Need a Boss?

The traditional model of medical delivery, in which the doctor is trained, respected, and compensated as an independent craftsman, is anachronistic. When a patient has multiple ailments, there is no longer a simple doctor-patient or doctor-patient-specialist relationship. Instead, there are multiple specialists who have an impact on the patient, each with a set of interdependencies and difficult coordination issues that increase exponentially with the number of ailments involved. Patients with multiple diagnoses require someone who can organize the efforts of multiple medical professionals. It is not unreasonable to imagine that delivering health care effectively, particularly for complex patients, could require a corporate model of organization. At least two forces stand in the way of robust competition from corporate health care providers. First is the regime of third-party fee-for-service payment, which is heavily entrenched by Medicare, Medicaid, and the regulatory and tax distortions that tilt private health insurance in the same direction. Consumers should control the money that purchases their health insurance, and should be free to choose their insurer and health care providers. Second, state licensing regulations make it difficult for corporations to design optimal work flows for health care delivery. Under institutional licensing, regulators would instead evaluate how well a corporation treats its patients, not the credentials of the corporation's employees. Alternatively, states could recognize clinician licenses issued by other states. That would let corporations operate in multiple states under a single set of rules and put pressure on states to eliminate unnecessarily restrictive regulations

Interpreting Instrumental Variables Estimates of the Returns to Schooling

This paper synthesizes economic insights from theoretical models of schooling choice based on individual benefits and econometric work interpreting instrumental variables estimates as weighted averages of individual-specific causal effects. Linkages are illustrated using college proximity to instrument for schooling. After characterizing groups differentially affected by the instrument according to family background, I directly compute weights underlying estimation of the overall return. In analyzing the level of schooling at which individuals change their behavior in response to the instrument, I demonstrate that this instrument has its greatest impact on the transition from high school to college. Specification robustness is also examined.