Showing papers by "Yu Huang published in 2009"

Rational Fabrication of Graphene Nanoribbons Using a Nanowire Etch Mask

Abstract: We report a rational approach to fabricate graphene nanoribbons (GNRs) with sub-10 nm width by employing chemically synthesized nanowires as the physical protection mask in oxygen plasma etch. Atomic force microscopy study shows that the patterns of the resulted nanoribbons replicate exactly those of mask nanowires so that ribbons or branched or crossed graphene nanostructures can be produced. Our study shows a linear scaling relation between the resulted GNR widths and mask nanowire diameters with variable slopes for different etching times. GNRs with controllable widths down to 6 nm have been demonstrated. We have fabricated GNR field effect transistors (FETs) with nanoribbons directly connected to bulk graphene electrodes. Electrical measurements on an 8 nm GNR-FET show room temperature transistor behavior with an on/off ratio around 160, indicating appreciable band gaps arise due to lateral confinement. We find the on/off ratio in the log scale inversely scales with ribbon width. This approach opens a...

Electrically conductive and optically active porous silicon nanowires.

Abstract: We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, to entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for novel optoelectronic devices for energy harvesting, conversion, and biosensing.

Anti-hypertensive nutraceuticals and functional foods.

Abstract: Epidemiological studies have demonstrated that elevated blood pressure is one of the major risk factors for stroke and coronary heart disease (CHD). A close association between blood pressure and the incidence of cardiovascular diseases is well established if systolic/diastolic blood pressure is above 140/90 mmHg. In recent years, nutraceuticals and functional foods have attracted considerable interest as potential alternative therapies for treatment of hypertension, especially for prehypertensive patients, whose blood pressure is marginally or mildly high but not high enough to warrant the prescription of blood pressure-lowering medications. This review summarizes the findings of recent studies on the chemistry, production, application, efficacy, and mechanisms of popular blood pressure-lowering nutraceuticals and functional foods including the Dietary Approaches to Stop Hypertension (DASH) diet plan, L-arginine, chlorogenic acid, fermented milk, garlic, onion, tea, soybean, ginger, hawthorn, and fish oil.

Cyclooxygenase-2–Derived Prostaglandin F2α Mediates Endothelium-Dependent Contractions in the Aortae of Hamsters With Increased Impact During Aging

Abstract: Hypertension and vascular dysfunction result in the increased release of endothelium-derived contracting factors (EDCFs), whose identity is poorly defined. We tested the hypothesis that endothelial cyclooxygenase (COX)-2 can generate EDCFs and identified the possible EDCF candidate. Changes in isometric tension of aortae of young and aged hamsters were recorded on myograph. Real-time changes in intracellular calcium concentrations ([Ca(2+)](i)) in native aortic endothelial cells were measured by imaging. Endothelium-dependent contractions were triggered by acetylcholine (ACh) after inhibition of nitric oxide production and they were abolished by COX-2 but not COX-1 inhibitors or by thromboxane-prostanoid receptor antagonists. 2-Aminoethoxydiphenyl borate (cation channel blocker) eliminated endothelium-dependent contractions and ACh-stimulated rises in endothelial cell [Ca(2+)](i). RT-PCR and Western blotting showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid chromatography-coupled mass spectrometry showed release of prostaglandin (PG)F(2alpha) and prostacyclin (PGI(2)) increased by ACh; only PGF(2alpha) caused contraction at relevant concentrations. COX-2 expression, ACh-stimulated contractions, and vascular sensitivity to PGF(2alpha) were augmented in aortae from aged hamsters. Human renal arteries also showed thromboxane-prostanoid receptor-mediated ACh- or PGF(2alpha)-induced contractions and COX-2-dependent release of PGF(2alpha). The present study demonstrates that PGF(2alpha), derived from COX-2, which is localized primarily in the endothelium, is the most likely EDCF underlying endothelium-dependent, thromboxane-prostanoid receptor-mediated contractions to ACh in hamster aortae. These contractions involved increases in endothelial cell [Ca(2+)](i). The results support a critical role of COX-2 in endothelium-dependent contractions in this species with an increased importance during aging and, possibly, a similar relevance in humans.

Interaction Between P450 Eicosanoids and Nitric Oxide in the Control of Arterial Tone in Mice

Abstract: Objective— Epoxyeicosatrienoic acids (EETs) serve as endothelial-derived hyperpolarizing factors (EDHF), but may also affect vascular function by other mechanisms. We identified a novel interaction between EETs and endothelial NO release using soluble epoxide hydrolase (sEH) −/− and +/+ mice. Methods and Results— EDHF responses to acetylcholine in pressurized isolated mesenteric arteries were neither affected by the sEH inhibitor, N-adamantyl-N′-dodecylurea (ADU), nor by sEH gene deletion. However, the EDHF responses were abolished by catalase and by apamin/charybdotoxin (ChTx), but not by iberiotoxin, nor by the cytochrome P450 inhibitor PPOH. All four EETs (order of potency: 8,9-EET >14,15-EET≈5,6-EET >11,12-EET) and all 4 dihydroxy derivatives (14,15-DHET≈8,9-DHET≈11,12-DHET >5,6-DHET) produced dose-dependent vasodilation. Endothelial removal or L-NAME blocked 8,9-EET and 14,15-DHET-dependent dilations. The effects of apamin/ChTx were minimal. 8,9-EET and 14,15-DHET induced NO production in endothelial cells. ADU (100 μg/mL in drinking water) lowered blood pressure in angiotensin II–infused hypertension, but not in L-NAME–induced hypertension. Blood pressure and EDHF responses were similar in L-NAME–treated sEH +/+ and −/− mice. Conclusions— Our data indicate that the EDHF response in mice is caused by hydrogen peroxide, but not by P450 eicosanoids. Moreover, P450 eicosanoids are vasodilatory, largely through their ability to activate endothelial NO synthase (eNOS) and NO release.

Berberine prevents hyperglycemia-induced endothelial injury and enhances vasodilatation via adenosine monophosphate-activated protein kinase and endothelial nitric oxide synthase.

Abstract: Aims Endothelial dysfunction is a key event that links obesity, diabetes, hypertension, and cardiovascular diseases. The aim of the present study was to examine the protective effect of the alkaloid drug berberine against hyperglycemia-induced cellular injury and endothelial dysfunction. Methods and results In both cultured endothelial cells and blood vessels isolated from rat aorta, berberine concentration dependently enhanced phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177 and promoted the association of eNOS with heat shock protein 90 (HSP90), leading to an increased production of nitric oxide. Furthermore, berberine attenuated high glucose-induced generation of reactive oxygen species, cellular apoptosis, nuclear factor-κB activation, and expression of adhesion molecules, thus suppressing monocyte attachment to endothelial cells. In mouse aortic rings, berberine elicited endothelium-dependent vasodilatations and alleviated high glucose-mediated endothelial dysfunction. All these beneficial effects of berberine on the endothelium were abolished by either pharmacological inhibition of adenosine monophosphate-activated protein kinase (AMPK) or adenovirus-mediated overexpression of a dominant negative version of AMPK. Conclusion Berberine protects against endothelial injury and enhances the endothelium-dependent vasodilatation, which is mediated in part through activation of the AMPK signalling cascade. Berberine or its derivatives may be useful for the treatment and/or prevention of endothelial dysfunction associated with diabetes and cardiovascular disease.

Protein Nanocapsule Weaved with Enzymatically Degradable Polymeric Network

Abstract: Target proteins can be functionally encapsulated using a cocoon-like polymeric nanocapsule formed by interfacial polymerization. The nanocapsule is cross-linked by peptides that can be proteolyzed by proteases upon which the protein cargo is released. The protease-mediated degradation process can be controlled in a spatiotemporal fashion through modification of the peptide cross-linker with photolabile moieties. We demonstrate the utility of this approach through the cytoplasmic delivery of the apoptosis inducing caspase-3 to cancer cells.

Exercise, vascular wall and cardiovascular diseases: an update (part 2).

Abstract: There is much evidence extolling the virtues of physical activity on cardiovascular disease (CVD). The evidence derives from different population groups where leisure time physical activity reduced the risk of coronary heart disease and cardiovascular mortality in both men and women. Recent meta-analyses have shown that large risk reductions for both ischaemic and haemorrhagic stroke can be achieved by moderate or intense physical activity. There are many data from human and animal studies confirming a beneficial role for exercise in the prevention and treatment of CVD. Physical inactivity and obesity/overweight are not only associated with a number of health-related risk factors, but are considered to be independent risk factors for CVD, type 2 diabetes mellitus and hypertension. Clinical trials confirm that lifestyle interventions (dietary modification and increased physical activity) reduce the risk of progressing from impaired glucose tolerance to type 2 diabetes. Moreover, epidemiological studies indicate that the risk of hypertension increases by being overweight. Modest increases in exercise intensity and frequency have hypotensive effects in sedentary hypertensive patients. Long-term training improves endothelium-dependent dilatation in the aorta and resistance arteries of the heart, whereas short-term training increases endothelial function in coronary conduit arteries. Overall, more scientific evidence will undoubtedly encourage the widespread advocacy of the clinical benefits of exercise therapy in the prevention and treatment of CVD.

Aerosol-assisted flow synthesis of B-doped, Ni-doped and B–Ni-codoped TiO2 solid and hollow microspheres for photocatalytic removal of NO

Abstract: In this study, highly effective B-doped, Ni-doped and B–Ni-codoped TiO2 microspheres photocatalysts were directly synthesized via an aerosol-assisted flow synthesis method. The resulting samples were characterized by XRD, SEM, TEM, UV–vis diffuse reflectance spectroscopy, nitrogen adsorption and XPS. The characterizations revealed hollow microspherical structure of the B-doped and B–Ni-codoped TiO2 photocatalysts, while the Ni-doped and undoped TiO2 products consisted of solid microspheres. It was found that the boron dopant was partially embedded into the interstitial TiO2 structure, existing in the form of Ti–O–B structure. The band gap was enlarged after the boron doping. However, both Ni-doped and B–Ni-codoped TiO2 samples showed obvious red shift in their absorption edges because of the Ni doping. The photocatalytic activities of these samples were evaluated on the photocatalytic removal of NO under simulated solar light irradiation. All the aerosol-assisted flow synthesized samples had much higher photocatalytic activities than P25 and the doped TiO2 microspheres exhibited enhanced photocatalytic activity than the undoped counterparts. More interestingly, the B–Ni-codoped TiO2 photocatalyst possessed superior photocatalytic activity to the as-prepared single doped TiO2 products. The enhanced photocatalytic activity was explained and the formation mechanisms of hollow and solid microspheres were also proposed on the basis of characterizations. We think this general method may be easily scaled up for industrial production of highly active microspherical photocatalysts for efficient NO removal under simulated solar light irradiation.

TRPC1 associates with BK(Ca) channel to form a signal complex in vascular smooth muscle cells.

Abstract: TRPC1 (transient receptor potential canonical 1) is a Ca(2+)-permeable cation channel involved in diverse physiological function. TRPC1 may associate with other proteins to form a signaling complex, which is crucial for channel function. In the present study, we investigated the interaction between TRPC1 and large conductance Ca(2+)-sensitive K(+) channel (BK(Ca)). With the use of potentiometric fluorescence dye DiBAC(4)(3), we found that store-operated Ca(2+) influx resulted in membrane hyperpolarization of vascular smooth muscle cells (VSMCs). The hyperpolarization was inhibited by an anti-TRPC1 blocking antibody T1E3 and 2 BK(Ca) channel blockers, charybdotoxin and iberiotoxin. These data were confirmed by sharp microelectrode measurement of membrane potential in VSMCs of intact arteries. Furthermore, T1E3 treatment markedly enhanced the membrane depolarization and contraction of VSMCs in response to several contractile agonists including phenylephrine, endothelin-1, and U-46619. In coimmunoprecipitation experiments, an antibody against BK(Ca) alpha-subunit [BK(Ca)(alpha)] could pull down TRPC1, and moreover an anti-TRPC1 antibody could reciprocally pull down BK(Ca)(alpha). Double-labeling immunocytochemistry showed that TRPC1 and BK(Ca) were colocalized in the same subcellular regions, mainly on the plasma membrane, in VSMCs. These data suggest that, TRPC1 physically associates with BK(Ca) in VSMCs and that Ca(2+) influx through TRPC1 activates BK(Ca) to induce membrane hyperpolarization. The hyperpolarizing effect of TRPC1-BK(Ca) coupling could serve to reduce agonist-induced membrane depolarization, thereby preventing excessive contraction of VSMCs to contractile agonists.

Choosing hamsters but not rats as a model for studying plasma cholesterol-lowering activity of functional foods

Abstract: Rats and hamsters are commonly used rodents to test the efficacy of cholesterol-lowering functional foods. In general, a diet containing 1% cholesterol for rats whereas a diet containing 0.1% cholesterol for hamsters is used to induce the hypercholesterolemia. The present study was carried out to compare hamsters with rats as a hypercholesterolemia model. Golden Syrian hamsters and Sprague Dawley rats were randomly divided into four groups and fed one of the four diets containing 0-0.9% cholesterol. Results demonstrated that serum total cholesterol (TC) in hamsters was raised 73-81% higher than that in rats fed the same cholesterol diets. Unlike rats in which HDL-C accounted very little for serum TC, the lipoprotein profile in hamsters was closer to that in humans. We investigated interaction of higher cholesterol diets with 3-hydroxy-3-methylglutary-CoA (HMG-CoA) reductase, low-density lipoprotein receptor (LDL-R) and cholesterol-7alpha-hydroxylase (CYP7A1), sterol regulatory element binding protein-2 (SREBP-2), and liver X receptor (LXR-alpha). Results showed hamsters and rats metabolized cholesterol differently. In view that hamsters synthesize and excrete cholesterol and bile acids in a manner similar to that in humans, it is concluded that hamsters but not rats shall be chosen as a model to study efficacy of cholesterol-lowering functional foods.

Specific peptide regulated synthesis of ultrasmall platinum nanocrystals.

Abstract: We demonstrate the rational synthesis of monodisperse ultrasmall platinum (Pt) nanocrsytals (NCs), in aqueous solution at room temperature, with specifically selected peptide molecules. The specific Pt-binding peptide, selected using a phage display technique, can function as a stabilizer to regulate Pt crystal nucleation and growth and, therefore, control both the morphology and size of the final Pt NCs. Uniform near-spherical Pt NCs with sizes ranging from 1.73 to 3.54 nm were achieved with a very narrow size distribution. The peptide-stabilized Pt NCs can be dispersed well in water for months. It was also demonstrated that the strong binding of peptides to the Pt NC surface is reversible by either pH modulation or peptide photolysis.

Protopanaxadiol and protopanaxatriol bind to glucocorticoid and oestrogen receptors in endothelial cells

Abstract: Background and purpose: Ginsenosides are used widely for medicinal purposes, but the mechanisms of their action are still unclear, although there is some evidence that these effects are mediated by nuclear receptors. Here we examined whether two metabolites of ginsenoside, protopanaxadiol (g-PPD) and protopanaxatriol (g-PPT), could modulate endothelial cell functions through the glucocorticoid receptor (GR) and oestrogen receptor (ER). Experiment approaches: The effects of g-PPD and g-PPT on intracellular calcium ion concentration ([Ca2+]i) and nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs) were measured using Fura-2-acetoxymethyl ester, 4-amino-5-methylamino-2′,7′-difluorofluorescein and Griess reagent. Effects on expression of GR and ER isoforms in HUVECs were determined using reverse transcriptase-/real-time PCR and immunocytochemistry. Phosphorylation of endothelial NO synthase (eNOS) was assessed by Western blotting. Results: Ginsenoside protopanaxadiol and g-PPT increased [Ca2+]i, eNOS phosphorylation and NO production in HUVECs, which were inhibited by the GR antagonist, RU486, the ER antagonist, ICI 182,780 and siRNA targeting GR or ERβ. The NO production was Ca2+-dependent and the [Ca2+]i elevation in HUVECs resulted from both intracellular Ca2+ release and extracellular Ca2+ influx. Conclusions and implications: Ginsenoside protopanaxadiol and g-PPT were functional ligands for both GR and ERβ, through which these ginsenoside metabolites exerted rapid, non-genomic effects on endothelial cells. Mandarin translation of abstract

All-polymer solar cells based on a blend of poly[3-(10-n-octyl-3-phenothiazine-vinylene)thiophene-co-2,5-thiophene] and poly[1,4-dioctyloxyl-p-2,5-dicyanophenylenevinylene]

Abstract: We report all-polymer solar cells (PSCs) based on a polymer blend of poly[3-(10-n-octyl-3-phenothiazine-vinylene)thiophene-co-2,5-thiophene] as donor and poly[1,4-dioctyloxyl-p-2,5-dicyanophenylenevinylene] as acceptor. Strong photoluminescence quenching is observed in the polymer blend indicating the photoinduced charge transfer occurs between the two polymers. The power conversion efficiency of the PSC was improved from 0.41% to 0.8% after 120 °C postannealing, under the illumination of AM 1.5, 100 mW/cm2. We attribute the improved efficiency to better morphological features of the photoactive layer after thermal annealing.

Scan Chain Diagnosis by Adaptive Signal Profiling with Manufacturing ATPG Patterns

Abstract: In the past, software based scan chain defect diagnosis can be roughly classified into two categories (1) model-based algorithms, and (2) data-driven algorithms. In this paper we first analyze the advantages and disadvantages of each category of the chain diagnosis algorithms. Next, an adaptive signal profiling algorithm that can use manufacturing ATPG scan patterns is proposed for scan chain diagnosis. Finally, several case studies and their PFA results are presented to validate the accuracy and effectiveness of the proposed algorithm.

System and method for enhancing the visibility of an object in a digital picture

Abstract: The visibility of an object in a digital picture is enhanced by comparing an input video of the digital picture with stored information representative of the nature and characteristics of the object to develop object localization information that identifies and locates the object. The visibility of the object and the region in which the object is located is enhanced by image processing and the enhanced input video is encoded.

Concerning the use of constant phase elements (CPEs) in the analysis of impedance data

Abstract: Impedance spectra obtained for Al6061 samples that had been anodized and sealed in two different processes and subjected to thermal cycling at three different temperatures have been analyzed using the Equivcrt software using a three-time constant model with four constant phase elements (CPEs). Excellent agreement has been observed between the experimental and the fit data. The high-frequency data have also been analyzed using the ANODAL software. Excellent agreement between the experimental data and the fit data was found in both cases; however, the fit parameters were quite different. The relationship between the CPEs and the surface properties of the anodized samples has been discussed.

Incorporation of Thienylenevinylene and Triphenylamine Moieties into Polythiophene Side Chains for All-Polymer Photovoltaic Applications

Abstract: We report all-polymer photovoltaic cells using poly(1,4-dioctyloxyl-p-2,5- dicyanophenylenevinylene) (DOCN-PPV) as electron acceptor and a series of polythiophene (PT) derivatives P1 to P3 as electron donors Among the polymer donors, P2 and P3 are new PT derivatives with functionalized and conjugated tri(thienylenevinylene) (TTV) and triphenylaminevinylene (TPAV) side chains, and they are characterized by absorption spectroscopy, cyclic voltammetry, and hole mobility, as well as morphology measurements Photovoltaic results indicate that the device performance is sensitive to the presence of functionalized side chains within the molecular structure To be specific, P1, without the functionalized side chains, yields the lowest power conversion efficiency (PCE) while P3, with both the TTV and TPAV side chains, shows a 2-fold increase in efficiency over P2 with only the TTV side chain, reaching a PCE of 044% under simulated AM 15 illumination at 100 mW/cm2 We attribute the enhancement of PCE to the impro

Test pattern generation for diagnosing scan chain failures

Abstract: Embodiments of the disclosed technology comprise techniques that can be used to generate scan chain test patterns and improve scan chain failure diagnosis resolution. For example, certain embodiments can be used to generate high quality chain diagnosis test patterns that are able to isolate a scan chain defect to a single scan cell. At least some embodiments can be used to locate faults over multiple capture cycles in the scan chain.

Self-aligned nanolithography in a nanogap.

Abstract: A self-aligned nanolithography approach is reported to form a nanoscale via hole in a nanogap. Field emission between two opposite electrodes of a nanogap is used to expose the polymer resist within the nanogap region. A via hole pattern forms in the nanogap area after the exposure process. The via hole pattern is obtained by ablating the polymer resists within the nanogap between two nanoelectrodes upon applying a certain bias voltage. The diameter of the via holes can be controlled to have comparable dimension to the nanogap width. Single or array of via holes have been demonstrated with variable diameters from 20 nm to over 100 nm. The self-aligned via nanoholes can be used to deposit functional nanostructures that are precisely aligned with the nanogap electrodes to form electrode−nanoisland−electrode tunneling junction devices. Electrical characterization of such devices shows typical tunneling characteristics at room temperature. These studies demonstrate a general pathway to making electrical conta...

Depth-image-based rendering

Abstract: Various implementations are described. Several implementations relate to depth-image-based rendering. Many of these implementations use temporal information in synthesizing an image. For example, temporal information may be used to generate a background layer for a warped image, and then the background layer may be blended with the main layer. One method includes accessing information from a reference image (1005). The reference image is for a reference view at a particular time. Information from a second image is accessed (1010). The second image is for a different time than the particular time. An additional image is created based on the information from the reference image and on the information from the second image (1015). The additional image is for an additional view that is different from the reference view and being for the particular time.

Fluid assisted assembly of one-dimensional nanoparticle array inside inorganic nanotubes

Abstract: We report a general method to assemble nanoparticle arrays inside inorganic nanotubes by introducing a nanoparticle solution into the nanotube nanochannels. We demonstrate that the size matching between nanotubes and nanoparticles may be used to form one-dimensional nanoparticle assemblies of variable sizes and configurations. Dark field scattering spectroscopy studies show large splitting of the resonance energy of the gold nanoparticle assembly under illumination with light with longitudinal or transverse polarization, indicating strong interparticle plasmon resonance coupling.

Antibiotic use in pulmonology wards of Chinese children’s hospitals: 2002–2006

Abstract: Summary Purpose: To investigate the pattern of antibiotic use in the pulmonology wards of four children’s hospitals in China from 2002 to 2006. Methods: The Anatomical Therapeutic Chemical Classification/Defined Daily Doses (ATC/DDD) methodology was used. Aggregate data on antibiotic use (ATC code-J01) were expressed in numbers of DDD/100 bed-days for inpatients. Results: The overall consumption of antibiotic drugs in the pulmonology wards of the four children’s hospitals were 83·7, 49·9, 53·6 and 79·3 DDD/100 bed-days, respectively. Injectables were among the most widely used antibiotics. In addition, there was a considerable variation in both the amount and the pattern of antibiotics used in the respective hospitals’ pulmonology wards. Conclusions: Wide variations were found between the four hospitals studied in the amount and type of antibiotics prescribed although the diseases treated appeared the same. This variation may have been due to differences in disease severity, regional diversity in bacterial resistance or variations in empiric treatment regimens. Despite the introduction of Chinese Ministry of Health Antibiotic Guidelines in 2004, the pattern of antibiotic use in individual hospitals remained unchanged from 2002 to 2006. Antibiotic utilization studies need be taken to the next level; comparing drugs used to treat specific diseases with guideline recommendations. In addition, educational and other interventions to ensure better compliance with guidelines are urgently required.

System and method for bit-allocation in video coding

Abstract: A system and method for region-of-interest-based bit-allocation scheme for video coding is provided. A method for encoding an image sequence of inter-frames and intra-frames includes grouping the inter-frames and the intra-frames in at least one group of pictures (GOP), and performing a frame-level bit-allocation to inter-frames and the intra-frames in the GOP. For each frame of the inter-frames and the intra-frames in the GOP, the method also includes partitioning the frame into a plurality of macroblocks, identifying macroblocks in the plurality of macroblocks as having regions of interest (ROI), and performing a macroblock level bit-allocation for the frame based on macroblocks identified as having ROI. The method further includes encoding the image sequence based on the bit-allocations, thereby producing an encoded image sequence, and outputting the encoded image sequence.