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Antimicrobial stewardship program (ASP) interventions, such as prospective audit and feedback (PAF), have been shown to reduce antimicrobial use and improve patient outcomes. However, the optimal approach to PAF is unknown.
We examined the impact of a high–intensity interdisciplinary rounds–based PAF compared to low–intensity PAF on antimicrobial use on internal medicine wards in a 400–bed community hospital.
Prior to the intervention, ASP pharmacists performed low–intensity PAF with a focus on targeted antibiotics. Recommendations were made directly to the internist for each patient. High–intensity, rounds–based PAF was then introduced sequentially to 5 internal medicine wards. This PAF format included twice–weekly interdisciplinary rounds, with a review of all internal medicine patients receiving any antimicrobial agent. Antibiotic use and clinical outcomes were measured before and after the transition to high–intensity PAF. An interrupted time–series analysis was performed adjusting for seasonal and secular trends.
With the transition from low–intensity to high–intensity PAF, a reduction in overall usage was seen from 483 defined daily doses (DDD)/1,000 patient days (PD) during the low–intensity phase to 442 DDD/1,000 PD in the high–intensity phase (difference, −42; 95% confidence interval [CI], −74 to −9). The reduction in usage was more pronounced in the adjusted analysis, in the latter half of the high intensity period, and for targeted agents. There were no differences seen in clinical outcomes in the adjusted analysis.
High–intensity PAF was associated with a reduction in antibiotic use compared to a low–intensity approach without any adverse impact on patient outcomes. A decision to implement high–intensity PAF approach should be weighed against the increased workload required.
The material culture of Mayapan (ca. A.D. 1250–1400), the last great capital city of the northern Maya lowlands, has often been described as “decadent.” Such descriptions, however, are highly subjective. In this chapter, we consider poverty and wealth at Mayapan from a perspective based in modern economics. We find that, as in modern societies, wealth (as measured by house size) at Mayapan fits a Pareto distribution. Nevertheless, compared to two Classic-period sites in Mexico—Palenque and Sayil—the distribution of wealth was more equal at Mayapan, suggesting that economic inequality was less extreme at the Postclassic city. One cause for the decadent material culture of Mayapan, therefore, was that the city was impoverished when compared to its Classic predecessors.
In this essay we analyze the magnitude and distribution of wealth at Mayapan and explore the implications of our findings for the general interpretation of the economy, society, and culture of that city. Mayapan, Yucatan, Mexico, is the largest and most important Maya archaeological site dating to the Late Postclassic period, and therefore inspires a lot of curiosity among archaeologists. Their interest is piqued because, founded by the legendary Kukulcan, Mayapan was the political capital of the largest and most powerful Maya state of its period. Because of its size and power, Mayapan also served as the social and cultural capital of the northern lowlands at the same time. Because it was a late prehistoric site, Mayapan was discussed in many historical chronicles from the early colonial period, and so we possess unusually detailed information about it.
The immobilization of DNA on passivated n-type InAs (100) surfaces has been
studied using X-ray and ultraviolet photoelectron spectroscopy. The benefits
of sulfur passivation using ammonium sulfide solution
((NH4)2S) for DNA immobilization were examined. The
XPS/UPS data carried out on non-functionalized and functionalized surfaces
demonstrate that the DNA probes reacted with the sulfur-passivated InAs
surface. The XPS data in combination with fluorescently-tagged DNA indicate
that the sulfur passivation process leads to a higher and more uniform
attachment of DNA over the surface compared to non-sulfur-passivated InAs
surfaces. The XPS data obtained immediately after sulfur passivation clearly
observes In-S bonding, with little or no As-S. In addition, the XPS spectra
of As 3d core-levels immediately after sulfur passivation shows that there
is a negligible amount of As-Ox, but the peak become considerable
after exposure to the aqueous DNA probe solution. The increase in
As-Ox is likely due to the presence of non-sulfur bonded As
atoms present on the surface. The presence of sulfur on the surface does
lead to the high areal density of attached ssDNA. This system forms the
basis of a DNA sensing system. While chemically passivating the surface
against oxidation and facilitating probe attachment, the changes in Fermi
level position were also monitored by UPS. UPS spectra show that the Fermi
level of a clean InAs surface is located ~0.6 eV above the valence band
maximum. The changes in electronic states induced by sulfur passivation and
the pinning of EF are discussed.
Chemical functionalization of bio-molecules, including hemin (an iron porphyrin) and bovine albumin onto Si (100) and GaAs (100) surfaces is reported. Spectroscopic ellipsometry analysis on the optical response of functionalized surfaces provides information on molecular coverage and effective thickness as well as the kinetics of surface attachment. Topographic features of the chemically functionalized surfaces are investigated by atomic force microscopy
The interaction of InN epitaxial films grown by r.f. plasma assisted molecular beam epitaxy with atomic hydrogen and nitrogen, produced by remote r.f. H2 and N2 plasmas, is investigated. InN strongly reacts with both atomic hydrogen and nitrogen yielding depletion of nitrogen and concurrent formation of In clusters. The impact of hydrogen treatments on the optical properties of InN is assessed using photoluminescence (PL). It is found that hydrogen suppresses the intense PL band peaked at approximately 0.7eV for the as-grown InN epitaxial layers, and results in the appearance of a new PL band whose peak energy and intensity increase with H-dose. The effect of exposure to atomic hydrogen and nitrogen on electrical properties of InN is investigated using Hall effect measurements. Atomic force microscopy is also used for studying the morphological changes of InN upon interaction with atomic hydrogen and nitrogen.
GaPyAs1-y/GaAs, GaAsySb1-y/GaSb and GaSbyAs1-y/GaAs superlattices (SLs) grown by MBE, by exposure of GaAs to phosphorus and antimonide fluxes, and by exposure of GaSb to an arsenic flux, respectively, have been investigated. The focus is on the abruptness of interfaces and understanding the mechanisms associated with anion incorporation and exchange. In the case of the Sb flux interaction with the GaAs surface, the Sb segregation at the GaAs surface inhibits anion exchange. For the case of As over GaSb reactions, anion exchange results in the formation not only of the ternary alloy GaAsySb1-y, but also of isoelectronic compounds AsSbx that segregate at the GaSb/GaAs interface. In the case of the P flux interfaction with the GaAs surface, fast in-diffusion of P results in graded GaPyAs1-y layer formation.
Herein, we discuss the use of a novel new substrate for III-Nitride epitaxy, Lithium Niobate. It is shown that Lithium Niobate (LN) has a smaller lattice mismatch to III-Nitrides than sapphire and can be used to control the polarity of III-Nitride films grown by plasma assisted molecular beam epitaxy. Results from initial growth studies are reported including using various nitridation/buffer conditions along with structural and optical characterization. Comparisons of data obtained from GaN and AlN buffer layers are offered and details of the film adhesion dependence on buffer layer conditions is presented. Lateral polarization heterostructures grown on periodically poled LN are also demonstrated. While work is still required to establish the limits of the methods proposed herein, these initial studies offer the promise for mixing III-Nitride semiconductor materials with lithium niobate allowing wide bandgap semiconductors to utilize the acoustic, pyroelectric/ferroelectric, electro-optic, and nonlinear optical properties of this new substrate material as well as the ability to engineer various polarization structures for future devices.
The use of dry hydrogen plasma etching is evaluated for determination of GaN polarity and critically compared to wet etching in NaOH. It is shown that hydrogen plasma etching is effective in revealing inversion domains (IDs) and some types of dislocations. This is because the surface morphology is unchanged by the hydrogen treatment, and, hence, the surface reactivity is not masked.
Radiative recombination processes in bulk InGaN grown by molecular beam epitaxy (MBE) on lithium gallate (LGO or LiGaO2) substrates were investigated using microscopic PL and time-resolved photoluminescence (TRPL). The improved structural quality resulting from a better lattice match of the LGO substrate to III-V nitride materials simplifies these investigations because well-defined composition phases can be analyzed for both homogeneous and phased separated InGaN samples. Epilayers of InGaN intentionally grown with and without indium segregation were studied. X-ray diffraction measurements showed that the homogeneous epilayer was high quality In0.208Ga0.702N and the segregated epilayer exhibited peaks corresponding to both In0.289Ga0.711N and In0.443Ga0.557N indicating the presence of higher In concentration regions in this sample. Spatially resolved photoluminescence spectra confirm the existence of these regions. The photoluminescence intensity decay is non-exponential for both samples and a stretched exponential fit to the decay data confirms the existence of local potential fluctuations in which carriers are localized before recombination.
The performance of III-Nitride based Light Emitting Diodes (LEDs), LASERs, GaN/AlGaN MODFETs (Modulation-doped Field Effect Transistors) and HEMTs (High Electron Mobility Transistors) have been improved dramatically over the past few years [1,2], despite the relatively poor material quality of GaN, as compared to GaAs, for example. The intrinsic properties of the materials system make it extremely well suited to both optoelectronic and microwave power transistor applications. Typically, GaN is grown on substrates such as GaAs, Al2O3 (sapphire) or SiC with large lattice mismatch. This has usually resulted in an extremely high defect density in the GaN layer. The growth of GaN on lithium gallate LiGaO2 (LGO) affords many advantages compared to all other available substrates. LGO offers the smallest average lattice mismatch of any available substrate for the Ill-nitrides. This facilitates the growth of high quality GaN directly on Lithium Gallate without the need for a defective buffer to decouple the strain associated with the large lattice mismatch of other substrates .
The effect of the initial nitridation of the sapphire substrate on the GaN crystal quality as a function of substrate temperature was studied. GaN layers were grown by plasma-assisted molecular beam epitaxy (MBE) on sapphire substrates nitridated at different substrate temperatures. A strong improvement in the GaN crystal quality was observed at 100 °C nitridation temperature. Symmetric (0004) and asymmetric (10-5) full widths at half maximum (FWHM) of the x-ray rocking curves were 136 and 261 arcsec, respectively. This compares to an x-ray rocking curve full width at half maximum of 818 arcsec (0004) for conventional MBE buffer conditions. For our conventional buffer conditions, sapphire substrates were exposed to a N plasma at temperatures above 500 °C for 10min and then 25~50nm buffers were deposited without annealing at high temperature. The low temperature nitridation also shows an enhancement of the lateral growth of the GaN, resulting in larger grain sizes. The largest grain size achieved was approximately 2.8μm, while the average grain size was approximately 2.4μm at 100 °C nitridation temperature.
Thin film compliant substrates can be used to extend the critical thickness in mismatched overlayers. A metastability model has been coupled with recent experimental strain relief data to determine the critical thickness of InGaAs epilayers grown on GaAs compliant substrates of variable thickness. The results of this model are also compared to other compliant substrate critical thickness models.
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