9,324 research outputs found

    The Courier Conundrum: The High Costs of Prosecuting Low-Level Drug Couriers and What We Can Do About Them

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    Since the United States declared its “War on Drugs,” federal enforcement of drug-trafficking crimes has led to increased incarceration and longer prison sentences. Many low-level drug couriers and drug mules have suffered disproportionately from these policies; they face mandatory punishments that vastly exceed their culpability. Drug couriers often lack substantial ties to drug-trafficking organizations, which generally recruit vulnerable individuals to act as couriers and mules. By using either threats of violence or promises of relatively small sums of money, these organizations convince recruits to overlook the substantial risks that drug couriers face. The current policies of pursuing harsh punishments for low-level couriers generate significant societal costs. These costs include not only monetary costs but also collateral damage imposed on both the couriers and innocent third parties. Further, these harsh policies fail to generate appreciable benefits or satisfy the goals of either retributive or utilitarian theories of punishment. This Note proposes a legislative amendment to the current importation statute that would create a carveout under which low-level drug couriers could be charged under a separate misdemeanor statute. The proposal lays out a number of criteria that drafters could use to identify lowlevel participants and exempt them from the stiff mandatory minimum sentences and the long-term consequences that accompany a felony drug conviction

    Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap

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    A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.Comment: 11 pages, 8 figures. CMS NOTE-2010/00

    Kinetic Heterogeneities in a Highly Supercooled Liquid

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    We study a highly supercooled two-dimensional fluid mixture via molecular dynamics simulation. We follow bond breakage events among particle pairs, which occur on the scale of the α\alpha relaxation time τα\tau_{\alpha}. Large scale heterogeneities analogous to the critical fluctuations in Ising systems are found in the spatial distribution of bonds which are broken in a time interval with a width of order 0.05τα0.05\tau_{\alpha}. The structure factor of the broken bond density is well approximated by the Ornstein-Zernike form. The correlation length is of order 100σ1100 \sigma_1 at the lowest temperature studied, σ1\sigma_1 being the particle size. The weakly bonded regions thus identified evolve in time with strong spatial correlations.Comment: 3 pages, 6 figure

    Identifying substitutional oxygen as a prolific point defect in monolayer transition metal dichalcogenides with experiment and theory

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    Chalcogen vacancies are considered to be the most abundant point defects in two-dimensional (2D) transition-metal dichalcogenide (TMD) semiconductors, and predicted to result in deep in-gap states (IGS). As a result, important features in the optical response of 2D-TMDs have typically been attributed to chalcogen vacancies, with indirect support from Transmission Electron Microscopy (TEM) and Scanning Tunneling Microscopy (STM) images. However, TEM imaging measurements do not provide direct access to the electronic structure of individual defects; and while Scanning Tunneling Spectroscopy (STS) is a direct probe of local electronic structure, the interpretation of the chemical nature of atomically-resolved STM images of point defects in 2D-TMDs can be ambiguous. As a result, the assignment of point defects as vacancies or substitutional atoms of different kinds in 2D-TMDs, and their influence on their electronic properties, has been inconsistent and lacks consensus. Here, we combine low-temperature non-contact atomic force microscopy (nc-AFM), STS, and state-of-the-art ab initio density functional theory (DFT) and GW calculations to determine both the structure and electronic properties of the most abundant individual chalcogen-site defects common to 2D-TMDs. Surprisingly, we observe no IGS for any of the chalcogen defects probed. Our results and analysis strongly suggest that the common chalcogen defects in our 2D-TMDs, prepared and measured in standard environments, are substitutional oxygen rather than vacancies

    Structural Probe of a Glass Forming Liquid: Generalized Compressibility

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    We introduce a new quantity to probe the glass transition. This quantity is a linear generalized compressibility which depends solely on the positions of the particles. We have performed a molecular dynamics simulation on a glass forming liquid consisting of a two component mixture of soft spheres in three dimensions. As the temperature is lowered (or as the density is increased), the generalized compressibility drops sharply at the glass transition, with the drop becoming more and more abrupt as the measurement time increases. At our longest measurement times, the drop occurs approximately at the mode coupling temperature TCT_C. The drop in the linear generalized compressibility occurs at the same temperature as the peak in the specific heat. By examining the inherent structure energy as a function of temperature, we find that our results are consistent with the kinetic view of the glass transition in which the system falls out of equilibrium. We find no size dependence and no evidence for a second order phase transition though this does not exclude the possibility of a phase transition below the observed glass transition temperature. We discuss the relation between the linear generalized compressibility and the ordinary isothermal compressibility as well as the static structure factor.Comment: 18 pages, Latex, 26 encapsulated postscript figures, revised paper is shorter, to appear in Phys. Rev.

    The potential energy landscape of a model glass former: thermodynamics, anharmonicities, and finite size effects

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    It is possible to formulate the thermodynamics of a glass forming system in terms of the properties of inherent structures, which correspond to the minima of the potential energy and build up the potential energy landscape in the high-dimensional configuration space. In this work we quantitatively apply this general approach to a simulated model glass-forming system. We systematically vary the system size between N=20 and N=160. This analysis enables us to determine for which temperature range the properties of the glass former are governed by the regions of the configuration space, close to the inherent structures. Furthermore, we obtain detailed information about the nature of anharmonic contributions. Moreover, we can explain the presence of finite size effects in terms of specific properties of the energy landscape. Finally, determination of the total number of inherent structures for very small systems enables us to estimate the Kauzmann temperature

    The Paradox of Power in CSR: A Case Study on Implementation

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    Purpose Although current literature assumes positive outcomes for stakeholders resulting from an increase in power associated with CSR, this research suggests that this increase can lead to conflict within organizations, resulting in almost complete inactivity on CSR. Methods A single in-depth case study, focusing on power as an embedded concept. Results Empirical evidence is used to demonstrate how some actors use CSR to improve their own positions within an organization. Resource dependence theory is used to highlight why this may be a more significant concern for CSR. Conclusions Increasing power for CSR has the potential to offer actors associated with it increased personal power, and thus can attract opportunistic actors with little interest in realizing the benefits of CSR for the company and its stakeholders. Thus power can be an impediment to furthering CSR strategy and activities at the individual and organizational level

    Dynamics of Highly Supercooled Liquids:Heterogeneity, Rheology, and Diffusion

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    Highly supercooled liquids with soft-core potentials are studied via molecular dynamics simulations in two and three dimensions in quiescent and sheared conditions.We may define bonds between neighboring particle pairs unambiguously owing to the sharpness of the first peak of the pair correlation functions. Upon structural rearrangements, they break collectively in the form of clusters whose sizes grow with lowering the temperature TT. The bond life time τb\tau_b, which depends on TT and the shear rate \gdot, is on the order of the usual structural or α\alpha relaxation time τα\tau_{\alpha} in weak shear \gdot \tau_{\alpha} \ll 1, while it decreases as 1/\gdot in strong shear \gdot\tau_{\alpha} \gg 1 due to shear-induced cage breakage. Accumulated broken bonds in a time interval (∌0.05τb\sim 0.05\tau_b) closely resemble the critical fluctuations of Ising spin systems. For example, their structure factor is well fitted to the Ornstein-Zernike form, which yields the correlation length Ο\xi representing the maximum size of the clusters composed of broken bonds. We also find a dynamical scaling relation, τb∌Οz\tau_b \sim \xi^{z}, valid for any TT and \gdot with z=4z=4 in two dimensions and z=2z=2 in three dimensions. The viscosity is of order τb\tau_b for any TT and \gdot, so marked shear-thinning behavior emerges. The shear stress is close to a limiting stress in a wide shear region. We also examine motion of tagged particles in shear in three dimensions. The diffusion constant is found to be of order τb−Μ\tau_b^{-\nu} with Îœ=0.75∌0.8\nu=0.75 \sim 0.8 for any TT and \gdot, so it is much enhanced in strong shear compared with its value at zero shear. This indicates breakdown of the Einstein-Stokes relation in accord with experiments. Some possible experiments are also proposed.Comment: 20pages (including figures

    Elastic electron deuteron scattering with consistent meson exchange and relativistic contributions of leading order

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    The influence of relativistic contributions to elastic electron deuteron scattering is studied systematically at low and intermediate momentum transfers (Q2≀30Q^2\leq 30 fm−2^{-2}). In a (p/M)(p/M)-expansion, all leading order relativistic π\pi-exchange contributions consistent with the Bonn OBEPQ models are included. In addition, static heavy meson exchange currents including boost terms and lowest order ÏÏ€Îł\rho\pi\gamma-currents are considered. Sizeable effects from the various relativistic two-body contributions, mainly from π\pi-exchange, have been found in form factors, structure functions and the tensor polarization T20T_{20}. Furthermore, static properties, viz. magnetic dipole and charge quadrupole moments and the mean square charge radius are evaluated.Comment: 15 pages Latex including 5 figures, final version accepted for publication in Phys.Rev.C Details of changes: (i) The notation of the curves in Figs. 1 and 2 have been clarified with respect to left and right panels. (ii) In Figs. 3 and 4 an experimental point for T_20 has been added and a corresponding reference [48] (iii) At the end of the text we have added a paragraph concerning the quality of the Bonn OBEPQ potential

    How Substitutional Point Defects in Two-Dimensional WS2_2 Induce Charge Localization, Spin-Orbit Splitting, and Strain

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    Control of impurity concentrations in semiconducting materials is essential to device technology. Because of their intrinsic confinement, the properties of two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are more sensitive to defects than traditional bulk materials. The technological adoption of TMDs is dependent on the mitigation of deleterious defects and guided incorporation of functional foreign atoms. The first step towards impurity control is the identification of defects and assessment of their electronic properties. Here, we present a comprehensive study of point defects in monolayer tungsten disulfide (WS2_2) grown by chemical vapor deposition (CVD) using scanning tunneling microscopy/spectroscopy, CO-tip noncontact atomic force microscopy, Kelvin probe force spectroscopy, density functional theory, and tight-binding calculations. We observe four different substitutional defects: chromium (CrW_{\text{W}}) and molybdenum (MoW_{\text{W}}) at a tungsten site, oxygen at sulfur sites in both bottom and top layers (OS_{\text{S}} top/bottom), as well as two negatively charged defects (CDs). Their electronic fingerprints unambiguously corroborate the defect assignment and reveal the presence or absence of in-gap defect states. The important role of charge localization, spin-orbit coupling, and strain for the formation of deep defect states observed at substitutional defects in WS2_2 as reported here will guide future efforts of targeted defect engineering and doping of TMDs
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