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

Essential Programs and Services Report of Findings: System Administration Component

SUMMARY This analysis of the System Administration component of Maine’s Essential Programs and Services school funding model was prepared for the Commissioner of Education as part of the ongoing review of the cost formula, as required by Maine statute. Specific elements for analysis were determined in collaboration with the Maine Department of Education

Preliminary Investigation of Maine Virtual Charter School Costs Relative to the Essential Programs and Services Funding Model

In 2015, the Maine State Legislature\u27s Joint Standing Committee on Education and Cultural Affairs commissioned the Maine Education Policy Research Institute (MEPRI) to study the state\u27s Essential Program and Services (EPS) K-12 education funding model in relationship to the funding for Maine\u27s two virtual charter schools. The study was initiated with a review of available literature and reports on virtual school funding in other states. Because the structure of Maine\u27s virtual schools differs from typical models in other states, most notably because core academic subject teachers are required to teach from one central physical location, further cost analysis was conducted using only Maine-­based data. The expenditure data available was from one school (Maine Connections Academy) in its first year of operation in 2014-­15. This limits the generalizability of the findings. Data were analyzed by categorizing the virtual school expenditures as much as was possible into nineteen separate components of Maine\u27s Essential Programs and Services funding model. In each category, the report first provides a qualitative description of how the virtual school carries out that type of work. This provides background to aid the reader in understanding how virtual schools operate, and in interpreting any differences in expenditures. Next the quantitative analysis for that cost category is detailed, followed by a concise summary of whether the expenditures for that category were higher, lower, or similar to the EPS cost model, unless inadequate data were available to make a determination. An appendix provides a summary of virtual school policies in other states

Summary Report: Essential Programs and Services Career and Technical Education Component Review

Background The Career and Technical Education (CTE) funding model was implemented in FY2019 after a lengthy period of development. The component was scheduled for a review in FY2020 and FY2021 as part of the ongoing cycle of analysis of all major components of Maine’s Essential Programs and Services (EPS) education cost model. Due to the breadth and complexity of the CTE funding model, and the fact that this is the first time it has been reviewed to see how it is being implemented in actual practice, the findings have been broken into several sections. Appendix A provides the overall plan of analyses, which were divided into two separate reports. The Part I report issued in summer 2021 included analyses related to student enrollment trends, including the impact of the Covid-19 pandemic on program enrollments, as well as analyses related to facilities and maintenance spending. The Part II report issued in March 2022 described the remainder of the analyses, which are divided into three distinct sections based on the source data used in each task. Section I presented findings that were derived from staffing data. Section 2 described patterns from expenditure data from the most recent pre-pandemic program year. Section 3 summarized results of a questionnaire that was administered to all CTEs to gather data that are not routinely collected. The data from the questionnaire responses were needed to address a series of questions posed by the “Maine CTE Subsidy Workgroup,” which was formed by Maine Administrators of Career & Technical Education (MACTE) and the Maine School Superintendent Association (MSSA). The Maine Department of Education (MDOE) agreed to include the questions in the research plan for the EPS component review contract with MEPRI. The research topics and questions came from the Maine Department of Education, prior reports by MEPRI and MDOE, and the MACTE/MSSA CTE Subsidy Workgroup as mentioned above. Some of the information was needed for decisions to be made by MDOE during the continuing implementation of the EPS CTE model. The adequacy of sub-components was evaluated. And in some cases updated model parameters were computed. Miscellaneous topics 2 and questions presented by the MACTE/MSSA Workgroup were also addressed. Additionally, relevant findings were presented to the LD 313 work group, which was established after the MEPRI research project was well underway. The materials prepared by MEPRI for the LD 313 work group are included as Appendix D. The current summary report is a compilation of the findings of the Part I and Part II reports together with a summary of the main findings and elaboration on data and analysis methods. It begins with an overall summary of our most pertinent findings in order to aid the reader in navigating the various sections of the report. A methods section describes the data and the analysis techniques used in the review. Finally, detailed findings are presented in two parts corresponding to the Part I and Part II reports previously submitted

Artifacts at 4.5 and 8.0 um in Short Wavelength Spectra from the Infrared Space Observatory

Spectra from the Short Wavelength Spectrometer (SWS) on ISO exhibit artifacts at 4.5 and 8 um. These artifacts appear in spectra from a recent data release, OLP 10.0, as spurious broad emission features in the spectra of stars earlier than ~F0, such as alpha CMa. Comparison of absolutely calibrated spectra of standard stars to corresponding spectra from the SWS reveals that these artifacts result from an underestimation of the strength of the CO and SiO molecular bands in the spectra of sources used as calibrators by the SWS. Although OLP 10.0 was intended to be the final data release, these findings have led to an additional release addressing this issue, OLP 10.1, which corrects the artifacts.Comment: 14 pages, AASTex, including 5 figures. Accepted by ApJ Letter

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

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ~10^-9 solar masses/year. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-micron feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-micron band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.Comment: Accepted for publication in MNRAS, 24 pages, 16 figure