Force and energy dissipation variations in non-contact atomic force spectroscopy on composite carbon nanotube systems

UHV dynamic force and energy dissipation spectroscopy in non-contact atomic force microscopy were used to probe specific interactions with composite systems formed by encapsulating inorganic compounds inside single-walled carbon nanotubes. It is found that forces due to nano-scale van der Waals interaction can be made to decrease by combining an Ag core and a carbon nanotube shell in the Ag@SWNT system. This specific behaviour was attributed to a significantly different effective dielectric function compared to the individual constituents, evaluated using a simple core-shell optical model. Energy dissipation measurements showed that by filling dissipation increases, explained here by softening of C-C bonds resulting in a more deformable nanotube cage. Thus, filled and unfilled nanotubes can be discriminated based on force and dissipation measurements. These findings have two different implications for potential applications: tuning the effective optical properties and tuning the interaction force for molecular absorption by appropriately choosing the filling with respect to the nanotube.Comment: 22 pages, 6 figure

Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud

In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars we have computed a grid of modust radiative-transfer models for a range of dust compositions, mass-loss rates, dust shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5$-$35-$\mu$m Spitzer infrared spectrograph (IRS) spectra and broadband photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range $\sim 8\times10^{-8}$ to $5\times10^{-6}$ M$_{\odot}\ \mathrm{yr}^{-1}$, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]$-$[15] versus [3.2]$-$[7] colour-colour diagram, is able to determine the fractional abundance of alumina in O-rich AGB stars.Comment: 22 pages, 17 figures, accepted MNRA

Health Care Reform Through Medicaid Managed Care: Tennessee (TennCare) as a Case Study and a Paradigm

TennCare is a Medicaid demonstration project that allows Tennessee to require all Medicaid beneficiaries to secure medical care through a mandatory managed care system. Enrollees contract with private managed care organizations ( MCOs\u27), which are responsible for organizing a network of care providers and delivering medical care to covered beneficiaries. Driven by rapidly escalating Medicaid costs, TennCare\u27s mandatory managed care program has succeeded in saving money for the state in its Medicaid program. To secure the federal waiver that allowed the program to proceed, the state included non-Medicaid-eligible uninsured and uninsurable residents as TennCare beneficiaries. Federal matching funds accrue for all TennCare expenditures, including those for non-Medicaid-eligible enrollees, but federal matching is subject to a global cap. Cost savings from managed care were to pay for the improved access. The program covers about 1.3 million persons, 38% of whom are non- Medicaid-eligibles. The Medicaid component of TennCare has been stable, but the non-Medicaid-eligible TennCare population has risen by about 41% in the last two fiscal years, stressing the fiscal capacity of the program. The Article provides background on the development of TennCare, describing the political effect of the federal matching (cooperative federalism) aspect of TennCare on both state-level and federal- level decisionmaking. The Article identifies what it describes as the political moral hazard dimensions of these federal-state partnerships on state political decisionmaking and the correlative lock-in effect of the program on the state. Federal matching funds make program enhancement appealing and make cutbacks extremely painful. The interaction of state and federal program incentives is considered in depth, and both the state responses (use of private funding and provider-focused taxation) and federal responses (limits on federal matching for those sources of state revenue) to these incentives are described and analyzed

Redefining Government\u27s Role in Health Care: Is a Dose of Competition What the Doctor Should Order?

Throughout the 1970s, the two major political parties espoused some form of national health insurance. Faced with a fiscal squeeze, however, the Carter Administration gave national health insurance a relatively low priority.The political movement for comprehensive national health insurance rests on an ideological commitment that the federal government should underwrite the cost of providing universal access to medical services. The objective is essentially redistributive in nature: equitable concerns for the disadvantaged loom as the major focus. The selective expansion of coverage to encompass those identified as needy and worthy, but only those so identified, is anathema to those who traditionally support broad national health insurance. These proponents would contend that a universal and comprehensive program is necessary to avoid a dual system of medical care delivery--one for the poor and another for then on poor. Advocates of a universal program would, in effect, compel the nonpoor to fund and participate in a governmentally sponsored program designed to benefit the poor so that the medical care system operated under government auspices would not be confined to lower income persons and, implicitly, stigmatized as welfare medicine of lower quality and lower status.The access gap between rich and poor-a disparity that underlay much of the political initiative for national health insurance-has been narrowed in recent years at least partly because of Medicaid and Medicare. Overall expenditures on medical services have escalated dramatically during the past two decades and occupy an increasingly large component of our national income. Few people would now maintain that aggregate medical care spending is substantially too low. To the contrary, skeptics point out that structural institutional relationships in the medical sector encourage ever-expanding medical expenditures. Coupled with a growing awareness of the importance of nonmedical factors in the promotion of health, this fact has led to general questioning whether individuals and society collectively are getting their money\u27s worth from surging medical services expenditures. Pragmatically, factors such as lifestyle have assumed a more visible role in affecting health status. Politically, the sense that illness is fortuitous has been challenged, which in turn has suggested a more tight-fisted response to claims for more munificent redistributive programs. Moreover, other pressing claims on public budgets and cries for tax relief have recently emerged. These nonhealth demands make less money available for public programs with strong redistributional orientations... This Article examines the market-oriented approach, describing what it is and what its rationale is. It then focuses on the problem of equity within the market system. In addition, the Article analyzes and evaluates prior regulatory experiences and examines the emerging directions of health policy. Finally, the Article considers selective developments from the perspective of the competitive alternative

Measurement of the photon structure function at <Q2><Q^{2}> of 279 GeV2GeV^{2}

Inclusive gamma gamma interactions to hadronic final states have been studied in the ALEPH data (taken from 1991 to 1995) where one scattered electron or positron is detected in the electromagnetic calorimeters. The event sample has been used to measure the hadronic photon structure function. at high Q**2

Shifts in Practice Based on Rapid Re-Housing for Rural Homelessness: An Exploratory Study of Micropolitan Homeless Service Provision

Based on interviews with rural homeless service providers, the authors examine in this practice note how policy has created shifts in practice for organizations serving homeless populations. Homeless individuals find a decreasing opportunity for assistance while awaiting Rapid Re-Housing. Some organizations, dependent on Rapid Re-Housing monies, are facing a lack of funding to pay for general homeless care provision. Organizations are creating care networks to address requirements of the new policy in addition to pooling resources in underserved areas

Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets

The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 μm. Temperature- and size-dependent values of volume- and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 μm. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered

Optical constants of silicon carbide for astrophysical applications. II. Extending optical functions from IR to UV using single-crystal absorption spectra

Laboratory measurements of unpolarized and polarized absorption spectra of various samples and crystal stuctures of silicon carbide (SiC) are presented from 1200--35,000 cm$^{-1}$ ($\lambda \sim$ 8--0.28 $\mu$m) and used to improve the accuracy of optical functions ($n$ and $k$) from the infrared (IR) to the ultraviolet (UV). Comparison with previous $\lambda \sim$ 6--20 $\mu$m thin-film spectra constrains the thickness of the films and verifies that recent IR reflectivity data provide correct values for $k$ in the IR region. We extract $n$ and $k$ needed for radiative transfer models using a new ``difference method'', which utilizes transmission spectra measured from two SiC single-crystals with different thicknesses. This method is ideal for near-IR to visible regions where absorbance and reflectance are low and can be applied to any material. Comparing our results with previous UV measurements of SiC, we distinguish between chemical and structural effects at high frequency. We find that for all spectral regions, 3C ($\beta$-SiC) and the $\vec{E}\bot \vec{c}$ polarization of 6H (a type of $\alpha$-SiC) have almost identical optical functions that can be substituted for each other in modeling astronomical environments. Optical functions for $\vec{E} \| \vec{c}$ of 6H SiC have peaks shifted to lower frequency, permitting identification of this structure below $\lambda \sim4\mu$m. The onset of strong UV absorption for pure SiC occurs near 0.2 $\mu$m, but the presence of impurities redshifts the rise to 0.33 $\mu$m. Optical functions are similarly impacted. Such large differences in spectral characteristics due to structural and chemical effects should be observable and provide a means to distinguish chemical variation of SiC dust in space.Comment: 46 pages inc. 8 figures and 2 full tables. Also 6 electronic-only data files. Accepted by Ap

Improved Quantum Hard-Sphere Ground-State Equations of State

The London ground-state energy formula as a function of number density for a system of identical boson hard spheres, corrected for the reduced mass of a pair of particles in a sphere-of-influence picture, and generalized to fermion hard-sphere systems with two and four intrinsic degrees of freedom, has a double-pole at the ultimate \textit{regular} (or periodic, e.g., face-centered-cubic) close-packing density usually associated with a crystalline branch. Improved fluid branches are contructed based upon exact, field-theoretic perturbation-theory low-density expansions for many-boson and many-fermion systems, appropriately extrapolated to intermediate densities, but whose ultimate density is irregular or \textit{random} closest close-packing as suggested in studies of a classical system of hard spheres. Results show substantially improved agreement with the best available Green-function Monte Carlo and diffusion Monte Carlo simulations for bosons, as well as with ladder, variational Fermi hypernetted chain, and so-called L-expansion data for two-component fermions.Comment: 15 pages and 7 figure