Xiaohua Xu - Academia.edu (original) (raw)

Papers by Xiaohua Xu

Research paper thumbnail of Long-term Exposure to Ambient Fine Particulate Pollution Induces Insulin Resistance and Mitochondrial Alteration in Adipose Tissue

Toxicological Sciences, 2011

We have previously shown that chronic exposure to ambient fine particulate matter (less than 2.5 ... more We have previously shown that chronic exposure to ambient fine particulate matter (less than 2.5 mm in aerodynamic diameter, PM 2.5) pollution in conjunction with high-fat diet induces insulin resistance through alterations in inflammatory pathways. In this study, we evaluated the effects of PM 2.5 exposure over a substantive duration of a rodent's lifespan and focused on the impact of longterm exposure on adipose structure and function. C57BL/6 mice were exposed to PM 2.5 or filtered air (FA) (6 h/day, 5 days/week) for duration of 10 months in Columbus, OH. At the end of the exposure, PM 2.5-exposed mice demonstrated insulin resistance (IR) and a decrease in glucose tolerance compared with the FA-exposed group. Although there were no significant differences in circulating cytokines between PM 2.5-and FA-exposed groups, circulating adiponectin and leptin were significantly decreased in PM 2.5exposed group. PM 2.5 exposure also led to inflammatory response and oxidative stress as evidenced by increase of Nrf2-regulated antioxidant genes. Additionally, PM 2.5 exposure decreased mitochondrial count in visceral adipose and mitochondrial size in interscapular adipose depots, which were associated with reduction of uncoupling protein 1 (UCP1) expression and downregulation of brown adipocyte-specific gene profiles. These findings suggest that long-term ambient PM 2.5 exposure induces impaired glucose tolerance, IR, inflammation, and mitochondrial alteration, and thus, it is a risk factor for the development of type 2 diabetes.

Research paper thumbnail of Association of systemic inflammation with marked changes in particulate air pollution in Beijing in 2008

Toxicology letters, Jan 20, 2012

Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5μm, ... more Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5μm, PM(2.5)) air pollution to increased morbidity and mortality of cardiovascular diseases in the general population, but the biologic mechanisms of these associations are yet to be elucidated. In this study, we aimed to evaluate the relationship between daily variations in exposure to PM(2.5) and inflammatory responses in mice during and for 2 months after the Beijing Olympic Games. Male C57BL/6 mice were exposed to Beijing PM(2.5) or filtered air (FA) in 2008 during the 2 months of Beijing Olympic and Paralympic Games, and for 2 months after the end of the Games. During the Games, circulating monocyte chemoattractant protein 1 and interleukin 6 were increased significantly in the PM(2.5) exposure group, when compared with the FA control group, although there were no significant inter-group differences in tumor necrosis factor-α or interferon-γ, or in macrophages, neutrophils or lymphocytes...

Research paper thumbnail of VLSI-Compatible Carbon Nanotube Doping Technique with Low Work-Function Metal Oxides

Nano Letters, 2014

Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for fut... more Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future highspeed transistor technology. However, as-made carbon nanotube field effect transistors (CNFETs) are p-type in ambient, and a consistent and reproducible n-type carbon nanotube (CNT) doping technique has yet to be realized. In addition, for very large scale integration (VLSI) of CNT transistors, it is imperative to use a solid-state method that can be applied on the wafer scale. Herein we present a novel, VLSI-compatible doping technique to fabricate n-type CNT transistors using low work-function metal oxides as gate dielectrics. Using this technique we demonstrate wafer-scale, aligned CNT transistors with yttrium oxide (Y 2 O x) gate dielectrics that exhibit n-type behavior with I on /I off of 10 6 and inverse subthreshold slope of 95 mV/dec. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) analyses confirm that slow (∼1 Å/s) evaporation of yttrium on the CNTs can form a smooth surface that provides excellent wetting to CNTs. Further analysis of the yttrium oxide gate dielectric using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques revealed that partially oxidized elemental yttrium content increases underneath the surface where it acts as a reducing agent on nanotubes by donating electrons that gives rise to n-type doping in CNTs. We further confirm the mechanism for this technique with other low work-function metals such as lanthanum (La), erbium (Er), and scandium (Sc) which also provide similar CNT NFET behavior after transistor fabrication. This study paves the way to exploiting a wide range of materials for an effective n-type carbon nanotube transistor for a complementary (p-and ntype) transistor technology.

Research paper thumbnail of Long-term Exposure to Ambient Fine Particulate Pollution Induces Insulin Resistance and Mitochondrial Alteration in Adipose Tissue

Toxicological Sciences, 2011

We have previously shown that chronic exposure to ambient fine particulate matter (less than 2.5 ... more We have previously shown that chronic exposure to ambient fine particulate matter (less than 2.5 mm in aerodynamic diameter, PM 2.5) pollution in conjunction with high-fat diet induces insulin resistance through alterations in inflammatory pathways. In this study, we evaluated the effects of PM 2.5 exposure over a substantive duration of a rodent's lifespan and focused on the impact of longterm exposure on adipose structure and function. C57BL/6 mice were exposed to PM 2.5 or filtered air (FA) (6 h/day, 5 days/week) for duration of 10 months in Columbus, OH. At the end of the exposure, PM 2.5-exposed mice demonstrated insulin resistance (IR) and a decrease in glucose tolerance compared with the FA-exposed group. Although there were no significant differences in circulating cytokines between PM 2.5-and FA-exposed groups, circulating adiponectin and leptin were significantly decreased in PM 2.5exposed group. PM 2.5 exposure also led to inflammatory response and oxidative stress as evidenced by increase of Nrf2-regulated antioxidant genes. Additionally, PM 2.5 exposure decreased mitochondrial count in visceral adipose and mitochondrial size in interscapular adipose depots, which were associated with reduction of uncoupling protein 1 (UCP1) expression and downregulation of brown adipocyte-specific gene profiles. These findings suggest that long-term ambient PM 2.5 exposure induces impaired glucose tolerance, IR, inflammation, and mitochondrial alteration, and thus, it is a risk factor for the development of type 2 diabetes.

Research paper thumbnail of Association of systemic inflammation with marked changes in particulate air pollution in Beijing in 2008

Toxicology letters, Jan 20, 2012

Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5μm, ... more Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5μm, PM(2.5)) air pollution to increased morbidity and mortality of cardiovascular diseases in the general population, but the biologic mechanisms of these associations are yet to be elucidated. In this study, we aimed to evaluate the relationship between daily variations in exposure to PM(2.5) and inflammatory responses in mice during and for 2 months after the Beijing Olympic Games. Male C57BL/6 mice were exposed to Beijing PM(2.5) or filtered air (FA) in 2008 during the 2 months of Beijing Olympic and Paralympic Games, and for 2 months after the end of the Games. During the Games, circulating monocyte chemoattractant protein 1 and interleukin 6 were increased significantly in the PM(2.5) exposure group, when compared with the FA control group, although there were no significant inter-group differences in tumor necrosis factor-α or interferon-γ, or in macrophages, neutrophils or lymphocytes...

Research paper thumbnail of VLSI-Compatible Carbon Nanotube Doping Technique with Low Work-Function Metal Oxides

Nano Letters, 2014

Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for fut... more Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future highspeed transistor technology. However, as-made carbon nanotube field effect transistors (CNFETs) are p-type in ambient, and a consistent and reproducible n-type carbon nanotube (CNT) doping technique has yet to be realized. In addition, for very large scale integration (VLSI) of CNT transistors, it is imperative to use a solid-state method that can be applied on the wafer scale. Herein we present a novel, VLSI-compatible doping technique to fabricate n-type CNT transistors using low work-function metal oxides as gate dielectrics. Using this technique we demonstrate wafer-scale, aligned CNT transistors with yttrium oxide (Y 2 O x) gate dielectrics that exhibit n-type behavior with I on /I off of 10 6 and inverse subthreshold slope of 95 mV/dec. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) analyses confirm that slow (∼1 Å/s) evaporation of yttrium on the CNTs can form a smooth surface that provides excellent wetting to CNTs. Further analysis of the yttrium oxide gate dielectric using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques revealed that partially oxidized elemental yttrium content increases underneath the surface where it acts as a reducing agent on nanotubes by donating electrons that gives rise to n-type doping in CNTs. We further confirm the mechanism for this technique with other low work-function metals such as lanthanum (La), erbium (Er), and scandium (Sc) which also provide similar CNT NFET behavior after transistor fabrication. This study paves the way to exploiting a wide range of materials for an effective n-type carbon nanotube transistor for a complementary (p-and ntype) transistor technology.