Adaptive Reuse of Religious Buildings and Schools in the US: Determinants of Project Outcomes

This study addresses factors that affect the outcomes of adaptive reuse of empty religious buildings and schools in the United States. Literature-driven observable factors expected to have an impact on project outcomes include both supply side and demand side factors (building characteristics, neighborhood demographics, micro-location characteristics, macro-economic factors, etc.) are used as explanatory variables. This study uses the multinomial logit model with the outcome of adaptive reuse projects (e.g., apartments, condominiums, retail, office and cultural uses) as the dependent variable. This study has found that many supply side and demand side factors are associated with certain outcomes. It is expected that the results of this study can offer valuable basic information about associations between factors and development outcomes for adaptive reuse.Adaptive reuse; Multinomial logit model; Religious buildings and schools

Mean-Field Theory for Interchain Orientational Ordering of Conjugated Polymers

We consider a generalized anisotropic planar-rotor model on a triangular lattice for interchain orientational ordering of undoped and doped polyacetylene, and investigate the effects of various terms on the symmetry and the range of stability of the observed herringbone (HB) phases. Dipole, quadrupole, and octopole interactions are included in the model with sixfold crystal-field anisotropy and are analyzed within the mean-field theory. The relative strength of these interactions can be estimated from the observed setting angle of the HB phase with the help of the smallness of crystal-field anisotropy. A model where the polymer chain is represented by a ‘‘quadrupolar’’ mass density only has various phases as the temperature and the interaction parameters are varied. Among them, the HB phase is found below a critical temperature Tc for some range of the parameter space, and the setting angle of the HB phase is 45° and independent of temperature. Competition between quadrupole and other interactions such as dipole or octopole, parametrized by the ratio of interaction strengths λ, results in an additional phase transition at T’c(λ) and makes the setting angle vary with the temperature below T’c(λ). For a model with quadrupole and octopole terms, there are two degenerate states of the setting angle related by θ’=π/2-θ. This degeneracy does not reflect a symmetry of the system and is lifted by the dipole terms. For a model with quadrupole and dipole interactions, the setting angle increases as the temperature is reduced below T’c(λ). From these results, we conclude that quadrupole and dipole interactions are important terms to explain experimental observations. Effects of crystal-field anisotropy resolve the twofold degeneracy, destroy the critical behavior associated with T’c(λ), and make the setting angle temperature dependent over the entire range of temperature below Tc. Crucial information on the interaction parameters of the model can be obtained through the temperature dependence of the setting angle of the HB phase

Brain oxygen responses induced by opioids: focus on heroin, fentanyl, and their adulterants

Opioids are important tools for pain management, but abuse can result in serious health complications. Of these complications, respiratory depression that leads to brain hypoxia is the most dangerous, resulting in coma and death. Although all opioids at large doses induce brain hypoxia, danger is magnified with synthetic opioids such as fentanyl and structurally similar analogs. These drugs are highly potent, act rapidly, and are often not effectively treated by naloxone, the standard of care for opioid-induced respiratory depression. The goal of this review paper is to present and discuss brain oxygen responses induced by opioids, focusing on heroin and fentanyl. In contrast to studying drug-induced changes in respiratory activity, we used chronically implanted oxygen sensors coupled with high-speed amperometry to directly evaluate physiological and drug-induced fluctuations in brain oxygen levels in awake, freely moving rats. First, we provide an overview of brain oxygen responses to physiological stimuli and discuss the mechanisms regulating oxygen entry into brain tissue. Next, we present data on brain oxygen responses induced by heroin and fentanyl and review underlying mechanisms. These data allowed us to compare the effects of these drugs on brain oxygen in terms of their potency, time-dependent response pattern, and potentially lethal effect at high doses. Then, we present the interactive effects of opioids during polysubstance use (alcohol, ketamine, xylazine) on brain oxygenation. Finally, we consider factors that affect the therapeutic potential of naloxone, focusing on dosage, timing of drug delivery, and contamination of opioids by other neuroactive drugs. The latter issue is considered chiefly with respect to xylazine, which strongly potentiates the hypoxic effects of heroin and fentanyl. Although this work was done in rats, the data are human relevant and will aid in addressing the alarming rise in lethality associated with opioid misuse

Oblique Angle Deposition of Germanium Film on Silicon Substrate

The effect of flux angle, substrate temperature and deposition rate on obliquely deposited germanium (Ge) films has been investigated. By carrying out deposition with the vapor flux inclined at 87° to the substrate normal at substrate temperatures of 250°C or 300°C, it may be possible to obtain isolated Ge nanowires. The Ge nanowires are crystalline as shown by Raman Spectroscopy.Singapore-MIT Alliance (SMA

Study of Stress Evolution of Germanium Nanocrystals Embedded in Silicon Oxide Matrix

Germanium (Ge) nanocrystals had been synthesized by annealing co-sputtered SiO₂-Ge in N₂ and/or forming gas (90% N₂ + 10% H₂) at temperatures ranging from 700 to 1000°C from 15 to 60 min. It was concluded that the annealing ambient, temperature and time have a significant influence on the formation and evolution of the nanocrystals. We also showed that a careful selective etching of the annealed samples in hydrofluoric solution enabled the embedded Ge nanocrystals to be liberated from the Si oxide matrix. From the Raman results of the as-grown and the liberated nanocrystals, we established that the nanocrystals generally experienced compressive stress in the oxide matrix and the evolution of these stress states was intimately linked to the distribution, density, size and quality of the Ge nanocrystals.Singapore-MIT Alliance (SMA

Charge storage in nanocrystal systems: Role of defects?

Wet thermal oxidations of polycrystalline Si₀.₅₄Ge₀.₄₆ films at 600°C for 30 and 50 min were carried out. A stable mixed oxide was obtained for films that were oxidized for 50 min. For film oxidized for 30 min, however, a mixed oxide with Ge nanocrystallites embedded in the oxide matrix was obtained. A trilayer gate stack structure that consisted of tunnel oxide/oxidized polycrystalline Si₀.₅₄Ge₀.₄₆/rf sputtered SiO₂ layers was fabricated. We found that with a 30 min oxidized middle layer, annealing the structure in N₂ ambient results in the formation of germanium nanocrystals and the annealed structure exhibits memory effect. For a trilayer structure with middle layer oxidized for 50 min, annealing in N₂ showed no nanocrystal formation and also no memory effect. Annealing the structures with 30 or 50 min oxidized middle layer in forming gas ambient resulted in nanocrystals embedded in the oxide matrix but no memory effect. This suggests that the charge storage mechanism for the trilayer structure is closely related to the interfacial traps of the nanocrystals.Singapore-MIT Alliance (SMA

Effect of Oxygen on Ni-Silicided FUSI Metal Gate

Continual evolution of the CMOS technology requires thinner gate dielectric to maintain high performance. However, when moving into the sub-65 nm CMOS generation, the traditional poly-Si gate approach cannot effectively reduce the gate thickness further due to the poly-depletion effect. Fully silicided metal gate (FUSI) has been proven to be a promising solution. FUSI metal gate can significantly reduce gate-line sheet resistance, eliminate boron penetration to channels and has good process compatibility with high-k gate dielectric. In this paper, the effect of oxygen introduced by the process of conventional furnace annealing in FUSI metal gate is investigated. A 120 nm amorphous Si layer was sputtered on dielectric oxides of various thicknesses grown using a standard oxidation process. Raman spectra showed that the 120 nm thick pre-sputtered amorphous Si recrystallized after annealing in a conventional furnace at 900°C. Secondary ion mass spectrometry (SIMS) revealed that the annealed Si film contained traces of oxygen which were incorporated into the film during the furnace annealing process. It is suspected that the oxygen was originated from a few ppm of impurities present in the high-purity annealing gas (N2). When a 100 nm of Ni was deposited using a DC sputterer on such sample and was rapid thermal annealed (RTA) at 400°C to form a fully silicide film, the transmission electron micrograph showed the existence of unreacted oxygen-rich Si layer along the interface of the NiSi/SiO2, leading to areal non-uniformity in the workfunction. It is suggested that the presence of oxygen can effectively retard the Ni diffusion into the Si film during the silicidation process such that the FUSI process is delayed, and the equivalent oxide thickness (EOT) increased as shown by capacitance-voltage (C-V) measurements. The workfunction of Ni-silicided FUSI film determined by C-V measurement on MOS structures was found to increase compared to the as-deposited amorphous Si film (the control sample).Singapore-MIT Alliance (SMA

Workfunction Tuning of n-Channel MOSFETs Using Interfacial Yttrium Layer in Fully Silicided Nickel Gate

Continual scaling of the CMOS technology requires thinner gate dielectric to maintain high performance. However, when moving into the sub-45 nm CMOS generation, the traditional poly-Si gate approach cannot effectively reduce the gate thickness further due to the poly-depletion effect. Fully silicided Ni metal gate (FUSI) has been proven to be a promising solution. Ni FUSI metal gate can significantly reduce gate-line sheet resistance, eliminate boron penetration to channels and has good process compatibility with high-k gate dielectric. But Ni FUSI has a mid-gap workfunction which is not suitable for high-performance CMOS applications where the band-edge workfunction is required. In this paper, we propose to tune the nickel (Ni) fully silicided metal gate (FUSI) workfunction via an yttrium/Si/Ni gate stack structure. The workfunction of such structure indicates that the Y interlayer can effectively tune the Ni FUSI workfunction from the mid gap to the conduction band edge of silicon by controlling the interlayer thickness. The gate stack workfunction starts to saturate to the pure yttrium value when the yttrium interlayer is >1.6 nm. This indicates the chemical potential of the material adjacent to gate electrode/gate insulator plays an important role in the determination of the workfunction.Singapore-MIT Alliance (SMA

Effects of Platinum on NiPtSiGe/n-SiGe and NiPtSi/n-Si Schottky Contacts

Solid phase reaction of NiPt/Si and NiPt/SiGe is one of the key issues for silicide (germanosilicide) technology. Especially, the NiPtSiGe, in which four elements are involved, is a very complex system. As a result, a detailed study is necessary for the interfacial reaction between NiPt alloy film and SiGe substrate. Besides using traditional material characterization techniques, characterization of Schottky diode is a good measure to detect the interface imperfections or defects, which are not easy to be found on large area blanket samples. The I-V characteristics of 10nm Ni(Pt=0, 5, 10 at.%) germanosilicides/n-Si₀/₇Ge₀.₃ and silicides/n-Si contact annealed at 400 and 500°C were studied. For Schottky contact on n-Si, with the addition of Pt in the Ni(Pt) alloy, the Schottky barrier height (SBH) increases greatly. With the inclusion of a 10% Pt, SBH increases ~0.13 eV. However, for the Schottky contacts on SiGe, with the addition of 10% Pt, the increase of SBH is only ~0.04eV. This is explained by pinning of the Fermi level. The forward I-V characteristics of 10nm Ni(Pt=0, 5, 10 at.%)SiGe/SiGe contacts annealed at 400°C were investigated in the temperature range from 93 to 300K. At higher temperature (>253K) and larger bias at low temperature (<253K), the I-V curves can be well explained by a thermionic emission model. At lower temperature, excess currents at lower forward bias region occur, which can be explained by recombination/generation or patches due to inhomogenity of SBH with pinch-off model or a combination of the above mechanisms.Singapore-MIT Alliance (SMA

Effect of Pt on agglomeration and Ge out-diffusion in Ni(Pt) germanosilicide

The effect of Ni and Ni(Pt) alloy with ~5 and 10 at. % Pt on the agglomeration and Ge out-diffusion in Nickel germanosilicide formed on Si&#x2080;.&#x2087;&#x2085;Ge&#x2080;.&#x2082;&#x2085;(100) has been studied. A remarkable improvement in the agglomeration behavior with increasing Pt atomic percentage is observed by sheet resistance measurements and scanning electron microscopy (SEM). In addition, x-ray diffraction (XRD) shows that only NiSiGe or Ni(Pt)SiGe phase exists from 400 to 800°C. However, Ge out-diffusion from the monogermanosilicide grains is obvious at 600°C and 700°C for Ni/SiGe and Ni(Pt)(Pt at.%~10%)/SiGe, respectively, evident by XRD and micro-Raman spectroscopy. The improved melting temperature of Ni(Pt)SiGe solution compared to that of NiSiGe is the likely reason of seeing better surface morphology and suppressing Ge out-diffusion of the germanosilicide grains observed.Singapore-MIT Alliance (SMA