122 research outputs found
Electrically Triggered Release of a Small Molecule Drug from a Polyelectrolyte Multilayer Coating
No full textAvailable in PMC 2011 December 14.Electrically triggered drug delivery represents an attractive option for actively and remotely controlling the release of a therapeutic from an implantable device (e.g., a “pharmacy-on-a-chip”). Here we report the fabrication of nanoscale thin films that can release precise quantities of a small molecule drug in response to application of a small, anodic electric potential of at least +0.5 V versus Ag/AgCl. Films containing negatively charged Prussian Blue (PB) nanoparticles and positively charged gentamicin, a small hydrophilic antibiotic, were fabricated using layer-by-layer (LbL) assembly. When oxidized, the PB nanoparticles shift from negatively charged to neutral, inducing dissolution of the film. Films with thicknesses in the range 100−500 nm corresponding to drug loadings of 1−4 μg/cm2 were characterized. We demonstrate control over the drug dosage by tuning the film thickness as well as the magnitude of the applied voltage. Drug release kinetics ranging from triggered burst release to on/off, or pulsatile release, were achieved by applying different electric potential profiles. Finally, the in vitro efficacy of the released drug was confirmed against Staphylococcus aureus bacteria. Given the versatility of an external electrical stimulus and the ability of the LbL assembly to conformally coat a variety of substrates regardless of size, shape, or chemical composition, we maintain that electrically controlled release of a drug from an LbL-coated surface could have applications in both implantable medical devices and transdermal drug delivery systems.National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award number DMR – 0819762)National Institute on Aging (grant number 5R01AG029601-03)National Institute of Dental and Craniofacial Research (U.S.) (grant number 5R01AG029601-03
Author Correction: Identifying genetic factors that contribute to the increased risk of congenital heart defects in infants with Down syndrome (Scientific Reports, (2020), 10, 1, (18051), 10.1038/s41598-020-74650-4)
No full text\ua9 2021, The Author(s).Ivan P. Moskowitz was omitted from the author list in the original version of this Article
The effectiveness of the controlled release of gentamicin from polyelectrolyte multilayers in the treatment of Staphylococcus aureus infection in a rabbit bone model
No full textWhile the infection rate of orthopedic implants is low, the required treatment, which can involve six weeks of antibiotic therapy and two additional surgical operations, is life threatening and expensive, and thus motivates the development of a one-stage re-implantation procedure. Polyelectrolyte multilayers incorporating gentamicin were fabricated using the layer-by-layer deposition process for use as a device coating to address an existing bone infection in a direct implant exchange operation. The films eluted about 70% of their payload in vitro during the first three days and subsequently continued to release drug for more than four additional weeks, reaching a total average release of over 550 μg/cm[superscript 2]. The coatings were demonstrated to be bactericidal against Staphylococcus aureus, and degradation products were generally nontoxic towards MC3T3-E1 murine preosteoblasts. Film-coated titanium implants were compared to uncoated implants in an in vivo S. aureus bone infection model. After a direct exchange procedure, the antimicrobial-coated devices yielded bone homogenates with a significantly lower degree of infection than uncoated devices at both day four (p < 0.004) and day seven (p < 0.03). This study has demonstrated that a self-assembled ultrathin film coating is capable of effectively treating an experimental bone infection in vivo and lays the foundation for development of a multi-therapeutic film for optimized, synergistic treatment of pain, infection, and osteomyelitis.National Institutes of Health (U.S.) (National Institute on Aging Grant 5R01AG029601-03
Local Overweighting and Underperformance: Evidence from Limited Partner Private Equity Investments
No full textInstitutional investors of all types exhibit substantial home-state bias when investing in private equity (PE) funds. This effect is particularly pronounced for public pension funds, where the local overweighting amounts to 9.7% of the private equity portfolio on average, based on 5-year rolling average benchmarks. Public pension funds’ own-state investments perform significantly worse than their out-of-state investments, an average of 3-4 percentage points of net IRR per year, and those that that overweight their portfolios towards home-state investments also perform worse overall. These underperformance patterns are not evident for other types of institutional investors, such as endowments, foundations and corporate pension funds, and we do not observe similar overweighting or underperformance of investments in neighboring states. Overweighting in home state investments by public pension funds is greater in states with higher levels of corruption, although there is no positive correlation of underperformance with corruption for these investors. The overweighting and underperformance of local investments cost public pension funds between 1.2 billion per year, depending on the benchmark.
The effect of pH on rates of reaction and hydrogen generation during serpentinization
No full text© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Solheid, P., & Moskowitz, B. The effect of pH on rates of reaction and hydrogen generation during serpentinization. Philosophical Transactions.Series A, Mathematical, Physical, and Engineering Sciences, 378(2165), (2020): 20180428, doi: 10.1098/rsta.2018.0428.A series of three laboratory experiments were conducted to investigate how pH affects reaction pathways and rates during serpentinization. Two experiments were conducted under strongly alkaline conditions using olivine as reactant at 200 and 230°C, and the results were compared with previous studies performed using the same reactants and methods at more neutral pH. For both experiments, higher pH resulted in more rapid serpentinization of the olivine and generation of larger amounts of H2 for comparable reaction times. Proportionally greater amounts of Fe were partitioned into brucite and chrysotile and less into magnetite in the experiments conducted at higher pH. In a third experiment, alkaline fluids were injected into an ongoing experiment containing olivine and orthopyroxene to raise the pH from circumneutral to strongly alkaline conditions. Increasing the pH of the olivine-orthopyroxene experiment resulted in an immediate and steep increase in H2 production, and led to far more extensive reaction of the primary minerals compared to a similar experiment conducted under more neutral conditions. The results suggest that the development of strongly alkaline conditions in actively serpentinizing systems promotes increased rates of reaction and H2 production, enhancing the flux of H2 available to support biological activity in these environments.This research was supported by the NASA Astrobiology Institute through Cooperative Agreement no. NNA15BB02A and NASA Solar Systems Workings program grant no. NNX16AL74G. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science
Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture
No full text© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Moskowitz, B., Berquo, T. S., Bach, W., & Templeton, A. S. Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture. Geochimica Et Cosmochimica Acta, 282, (2020): 55-75, doi:10.1016/j.gca.2020.05.016.A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.This research was supported by the U. S. National Science Foundation Marine Geology and Geophysics program through grant NSF-OCE 0927744 and by the NASA Astrobiology Institute through Cooperative Agreement NNA15BB02A. Additional support to TMM from the Hanse Wissenschaftskolleg (Delmenhorst, Germany) at an early stage of this project is gratefully acknowledged. FK acknowledges support through Grant NSF-OCE 1427274. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science. This is IRM contribution 1711. We very much appreciate the comments of Fabrice Brunet, Gleb Pokrovski and an anonymous reviewer that helped us refine our interpretations and improve communication of the results
A Coal Fired Gas Turbine Using An Air Cooled Fluidized Bed Combustor
No full textThe Society shall not be responsible for statements or opinions advanced in papers or in discussion at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the paper is published In an ASME Journal. `!^ ( Released for general publication upon presentation. Full credit should be given to ASME, the Technical Division, and the author($). Papers are available from ASME for nine months after the meeting
Conjugate convolutions and inner invariant means
No full textAbstractFor locally compact groups G, the author introduced a notion of [IA] groups, if there exists an inner invariant mean on G. The purpose of this paper is to characterize [IA] groups by introducing the so-called conjugate convolution operators which develop the techniques of the usual convolution operators. One of the characterizations of [IA] groups obtained in this paper is that a locally compact group G is [IA] if and only if for any finitely many conjugate convolution operators τ1(f1), τ1(f2), …, τ1(fn) on L1(G), L1(G) admits a family of positive functions of norm 1 on which the effects of τ1(f1), τ1(f2),…, τ1(fn) can be approximated by scalar multiplications by ∝Gfidλ correspondingly. Based on one of our results it follows that every [IN] group, introduced by S. Grosser, M. Moskowitz, and R. Mosak, is an [IA] group
Entrepreneurship and the Theory of Taxation
No full textTaxation theory rarely takes entrepreneurship into consideration. We discuss how this omission affects conclusions derived from standard models of capital taxation when applied to entrepreneurial income. Some of the defining features of entrepreneurship often omitted by standard capital taxation theory are incorporated into the analysis. This includes the lack of a well-functioning external market for entrepreneurial effort, limited access to external capital and the complementarities between entrepreneurial effort, entrepre-neurial innovation and capital investment. Because of these constraints, the entrepreneurial project is tied to the individual owner-manager. Unlike the typical passive portfolio investor assumed in cost of capital models the entrepreneur is unable to decouple savings decisions from investment decisions, and due to the comple-mentarities in production makes a joint decision on the supply of effort and capital. The returns from success-ful entrepreneurial ventures thus cannot be readily divided into labor and capital income, in stark contrast to what is assumed in standard taxation theory. When unique attributes of entrepreneurship are taken into account, some major conclusions of capital taxation models no longer hold, including the neutrality of capital taxation in owner-managed firms. These results are particularly important for the Nordic system of dual taxation, the theoretical foundation of which relies on the ability to neatly separate capital income from the labor income of the self-employed.Capital Income Taxation; Dual Income Taxation; Entrepreneurship; Innovation; Institutions; Labor Supply; New Firm Creation; Optimal Factor Taxes; Taxation; Tax Policy
International Financial Remoteness and Macroeconomic Volatility
No full textThis paper shows that proximity to major international financial centers seems to reduce business cycle volatility. In particular, we show that countries that are further from major locations of international financial activity systematically experience more volatile growth rates in both output and consumption, even after accounting for political institutions, trade, and other controls. Our results are relatively robust in the sense that more financially remote countries are more volatile, though the results are not always statistically significant. The comparative strength of this finding is in contrast to the more ambiguous evidence found in the literature.
- …
