| 701. |
- Wissmar, S. G. E., et al.
(författare)
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SiGe quantum well thermistor materials
- 2008
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 517:1, s. 337-339
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Tidskriftsartikel (refereegranskat)abstract
- A novel monocrystalline high-performance thermistor material based on SiGe quantum well (QW) heterostructures is presented. A comparison between different growth temperatures for Si0.7Ge0.3 and Si growth is performed. Results illustrate a value of 2.3%/K for TCR with a low excess noise.
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| 702. |
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| 703. |
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| 704. |
- Wong, Henry M. P., et al.
(författare)
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Donor and Acceptor Behavior in a Polyfluorene for Photovoltaics
- 2007
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Ingår i: J. Phys. Chem. C FIELD Full Journal Title:Journal of Physical Chemistry C. ; 111:13, s. 5244-5249
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Tidskriftsartikel (refereegranskat)abstract
- The authors study photovoltaic devices based on a red-absorbing conjugated polymer poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)) (APFO-3). The polymer acts as an electron donor when blended with ZnO nanoparticles, giving a short-circuit quantum efficiency of 28%. When blended with poly(3-hexylthiophene) (P3HT), however, the APFO-3 acts as an electron acceptor, giving a short-circuit quantum efficiency of 12%. The authors study this charge-transfer process by comparing photoinduced absorption spectra of the hybrid blends with the absorption spectra of chem. doped APFO-3, which allows one to distinguish features due to pos. and neg. polarons. The authors also present dark current measurements of single-carrier devices which demonstrate that APFO-3 has similar mobilities for electrons and holes, consistent with ambipolar behavior in photovoltaic devices. [on SciFinder (R)]
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| 705. |
- Wu, Richard You, et al.
(författare)
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Human Milk Oligosaccharides Increase Mucin Expression in Experimental Necrotizing Enterocolitis
- 2019
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Ingår i: Molecular Nutrition & Food Research. - : WILEY. - 1613-4125 .- 1613-4133. ; 63:3
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Tidskriftsartikel (refereegranskat)abstract
- Scope Necrotizing enterocolitis (NEC) is a leading cause of morbidity and death in preterm infants, occurring more often in formula-fed than breastfed infants. Studies in both rats and humans show that human milk oligosaccharides (HMOs) lower the incidence of NEC, but the mechanism underlying such protection is currently unclear. Methods and Results By extracting HMOs from pooled human breastmilk, the impact of HMOs on the intestinal mucin levels in a murine model of NEC are investigated. To confirm the results, the findings are validated by exposing human intestinal epithelial cells and intestinal organoids to HMOs and evaluated for mucin expression. HMO-gavage to pups increases Muc2 levels and decreases intestinal permeability to macromolecular dextran. HMO-treated cells have increased Muc2 expression, decreased bacterial attachment and dextran permeability during challenge by enteric pathogens. To identify the mediators involved in HMO induction of mucins, it is demonstrated that HMOs directly induce the expression of chaperone proteins including protein disulfide isomerase (PDI). Suppression of PDI activity removes the protective effects of HMOs on barrier function in vitro as well as NEC protection in vivo. Conclusions Taken together, the results provide insights to the possible mechanisms by which HMOs protect the neonatal intestine through upregulation of mucins.
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| 706. |
- Wu, Richard Y., et al.
(författare)
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Variations in the Composition of Human Milk Oligosaccharides Correlates with Effects on Both the Intestinal Epithelial Barrier and Host Inflammation : A Pilot Study
- 2022
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Ingår i: Nutrients. - : MDPI. - 2072-6643. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Human milk oligosaccharides are complex, non-digestible carbohydrates that directly interact with intestinal epithelial cells to alter barrier function and host inflammation. Oligosaccharide composition varies widely between individual mothers, but it is unclear if this inter-individual variation has any impact on intestinal epithelial barrier function and gut inflammation. Methods: Human milk oligosaccharides were extracted from the mature human milk of four individual donors. Using an in vitro model of intestinal injury, the effects of the oligosaccharides on the intestinal epithelial barrier and select innate and adaptive immune functions were assessed. Results: Individual oligosaccharide compositions shared comparable effects on increasing transepithelial electrical resistance and reducing the macromolecular permeability of polarized (Caco-2Bbe1) monolayers but exerted distinct effects on the localization of the intercellular tight junction protein zona occludins-1 in response to injury induced by a human enteric bacterial pathogen Escherichia coli, serotype O157:H7. Immunoblots showed the differential effects of oligosaccharide compositions in reducing host chemokine interleukin 8 expression and inhibiting of p38 MAP kinase activation. Conclusions: These results provide evidence of both shared and distinct effects on the host intestinal epithelial function that are attributable to inter-individual differences in the composition of human milk oligosaccharides.
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| 707. |
- Xenopoulos, Marguerite A., et al.
(författare)
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How humans alter dissolved organic matter composition in freshwater: relevance for the Earth’s biogeochemistry
- 2021
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Ingår i: Biogeochemistry. - : Springer Nature. - 0168-2563 .- 1573-515X. ; 154:2, s. 323-348
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic matter (DOM) is recognized for its importance in freshwater ecosystems, but historical reliance on DOM quantity rather than indicators of DOM composition has led to an incomplete understanding of DOM and an underestimation of its role and importance in biogeochemical processes. A single sample of DOM can be composed of tens of thousands of distinct molecules. Each of these unique DOM molecules has their own chemical properties and reactivity or role in the environment. Human activities can modify DOM composition and recent research has uncovered distinct DOM pools laced with human markers and footprints. Here we review how land use change, climate change, nutrient pollution, browning, wildfires, and dams can change DOM composition which in turn will affect internal processing of freshwater DOM. We then describe how human-modified DOM can affect biogeochemical processes. Drought, wildfires, cultivated land use, eutrophication, climate change driven permafrost thaw, and other human stressors can shift the composition of DOM in freshwater ecosystems increasing the relative contribution of microbial-like and aliphatic components. In contrast, increases in precipitation may shift DOM towards more relatively humic-rich, allochthonous forms of DOM. These shifts in DOM pools will likely have highly contrasting effects on carbon outgassing and burial, nutrient cycles, ecosystem metabolism, metal toxicity, and the treatments needed to produce clean drinking water. A deeper understanding of the links between the chemical properties of DOM and biogeochemical dynamics can help to address important future environmental issues, such as the transfer of organic contaminants through food webs, alterations to nitrogen cycling, impacts on drinking water quality, and biogeochemical effects of global climate change.
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| 708. |
- Xie, L., et al.
(författare)
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Strained Si0.2ge0.8/ge multilayer stacks epitaxially grown on a low-/high-temperature ge buffer layer and selective wet-etching of germanium
- 2020
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:9, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- With the development of new designs and materials for nano-scale transistors, vertical Gate-All-Around Field Effect Transistors (vGAAFETs) with germanium as channel materials have emerged as excellent choices. The driving forces for this choice are the full control of the short channel effect and the high carrier mobility in the channel region. In this work, a novel process to form the structure for a VGAA transistor with a Ge channel is presented. The structure consists of multilayers of Si0.2Ge0.8/Ge grown on a Ge buffer layer grown by the reduced pressure chemical vapor deposition technique. The Ge buffer layer growth consists of low-temperature growth at 400 °C and high-temperature growth at 650 °C. The impact of the epitaxial quality of the Ge buffer on the defect density in the Si0.2Ge0.8/Ge stack has been studied. In this part, different thicknesses (0.6, 1.2 and 2.0 µm) of the Ge buffer on the quality of the Si0.2Ge0.8/Ge stack structure have been investigated. The thicker Ge buffer layer can improve surface roughness. A high-quality and atomically smooth surface with RMS 0.73 nm of the Si0.2Ge0.8/Ge stack structure can be successfully realized on the 1.2 µm Ge buffer layer. After the epitaxy step, the multilayer is vertically dry-etched to form a fin where the Ge channel is selectively released to SiGe by using wet-etching in HNO3 and H2O2 solution at room temperature. It has been found that the solution concentration has a great effect on the etch rate. The relative etching depth of Ge is linearly dependent on the etching time in H2O2 solution. The results of this study emphasize the selective etching of germanium and provide the experimental basis for the release of germanium channels in the future. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 709. |
- Xiong, W., et al.
(författare)
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SiN-based platform toward monolithic integration in photonics and electronics
- 2021
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 32, s. 1-18
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Forskningsöversikt (refereegranskat)abstract
- This work presents a review of silicon nitride applications in Si photonics and electronics. As the one of the prominent photonics platform, it owes excellent characteristics in optical communication that is complimentary in performance to the silicon-on-insulator (SOI) photonics. In addition, silicon nitride plays also an important role in realizing germanium laser because of its unique behavior in tuning strain. The induced strain varies from high tensile to compressive stress. The induced strain improves the carrier transport in the channel of nFETs or pFETs. The strain provides also the possibility in adjusting the bandstructure of germanium and converts the germanium from indirect-to-direct band-gap material which is fundamental in obtain germanium laser.
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| 710. |
- Xu, Xinfeng, et al.
(författare)
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CLASSY III. The Properties of Starburst-driven Warm Ionized Outflows
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 933:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of analyses of galactic outflows in a sample of 45 low-redshift starburst galaxies in the COS Legacy Archive Spectroscopic SurveY (CLASSY), augmented by five additional similar starbursts with Cosmic Origins Spectrograph (COS) data. The outflows are traced by blueshifted absorption lines of metals spanning a wide range of ionization potential. The high quality and broad spectral coverage of CLASSY data enable us to disentangle the absorption due to the static interstellar medium (ISM) from that due to outflows. We further use different line multiplets and doublets to determine the covering fraction, column density, and ionization state as a function of velocity for each outflow. We measure the outflow's mean velocity and velocity width, and find that both correlate in a highly significant way with the star formation rate, galaxy mass, and circular velocity over ranges of four orders of magnitude for the first two properties. We also estimate outflow rates of metals, mass, momentum, and kinetic energy. We find that, at most, only about 20% of silicon created and ejected by supernovae in the starburst is carried out in the warm phase we observe. The outflows' mass-loading factor increases steeply and inversely with both circular and outflow velocity (log–log slope ∼−1.6), and reaches ∼10 for dwarf galaxies. We find that the outflows typically carry about 10%–100% of the momentum injected by massive stars and about 1%–20% of the kinetic energy. We show that these results place interesting constraints on, and new insights into, models and simulations of galactic winds.
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