Search Results - (Author, Cooperation:Y. M. Huang)

2012-08-10

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

The MEVVA ion source presented in the present paper adopts the arc discharge mechanism with a cathode changeable by a motor for pushing in, and an accel–decel three-grid extraction system. The voltage proof level is higher than 60 kV, the ion source generally runs at a voltage of 40 kV, the average beam current is higher than 5 mA, the beam spot is about 150 mm in diameter, and the nonuniformity of beams is within ±20%. Measurements of the beam radial profile show that there is a platform of about 40 mm in diameter in the central region. Ion beams and their optimal operation conditions for the cathode materials Al, Ti, Cr, Fe, Ni, Cu, Y, Zr, Mo, Ta, W, C, LaB6, etc., have already been obtained.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

After oxidation promoted by gamma-ray irradiation, in the photoluminescence (PL) spectra of Sm doped porous silicon (PS), there are three sharp peaks, superimposed on a broad band, with wavelengths near to those of the Sm doped SiO2 [R. Morimo, T. Mizushima, and H. Okumura, J. Electrochem. Soc. 137, 2340 (1990)]. The experimental results indicate that Sm-related luminescence centers can be created within the oxide of porous silicon, and only in porous silicon with high porosity can the Sm-related luminescence be found in the SiO2 layer. This experimental result can be explained by the fact that the excitation of electron-hole pairs occurs in nanoscale silicon, and the recombination occurs at the Sm-related luminescence centers in SiO2 layers covering nanoscale silicon.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

In this letter, we report the results of copper-doped porous silicon. In the photoluminescence spectrum of porous silicon without Cu doping, only one red luminescence band appears with a peak at 676.5 nm; while in the photoluminescence spectrum of Cu-doped porous silicon, red and near infrared luminescence bands appear with peaks at 660.6 and 802.2 nm, respectively. Energy dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy indicate the near infrared luminescence band is related to copper impurity in porous silicon. We assign the red luminescence band to band-to-band emission, and the near infrared luminescence band to band-to-acceptor emission. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

It has been shown that a two-peak green photoluminescence (PL) of porous silicon (PS) can be obtained from a continuous blueshift of a red PL by positron irradiation. At room temperature, PS samples were irradiated in air by energetic positrons coming from the conventionally used isotope 22Na (∼20 μCi). With increasing positron irradiation time, an originally red PL shifted continuously to green, then a two-peak PL appeared with a weak high-energy emission band (529 nm) and a low-energy dominant band (562 nm). The intensity of this high-energy band was enhanced by prolonged positron irradiation. The electron-spin-resonance signal combined with infrared absorption showed that positron irradiation created dangling bonds and stimulated oxide growth in PS. An interpretation is given on the basis of quantum confinement and atomiclike nature for very small nano-Si crystallites. © 1997 American Institute of Physics.

Electronic Resource

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The nuclear receptor heterodimers of liver X receptors (LXRs) are recently identified as key transcriptional regulators of genes involved in lipid homeostasis and inflammation. LXRs and their ligands are negative regulators of macrophage inflammatory gene expression. Multiple sclerosis (MS), a demyelinating disease of the central nervous system of unknown cause, is characterized by recurrent inflammation involving macrophages and their inflammatory mediators. Sweden belongs to the countries with a high MS incidence. In Italy, incidence is lower, with an exception for Sardinia where the incidence is even higher than that in Sweden. Subjects from Sardinia are ethnically more homogeneous and differ from Swedes, also regarding genetic background and environment. We studied LXRs and their related molecules of blood mononuclear cells (MNCs) from female patients with untreated relapsing-remitting MS from Sassari, Sardinia and Stockholm, Sweden. Sex- and age-matched healthy controls (HCs) were from both areas. mRNA expression was evaluated by real-time PCR. LXR-α was lower (P 〈 0.05) in MS (mean ± SEM: 3.1 ± 0.2; n = 37) compared to HC (3.6 ± 0.1; n = 37). LXR-α was lower in MS from Stockholm (2.6 ± 0.2; n = 22) compared to corresponding HC (3.4 ± 0.1; n = 22; P 〈 0.01) and compared to MS (3.8 ± 0.2; n = 15; P 〈 0.001) and HC (4 ± 0.2; n = 15; P 〈 0.001) from Sardinia. MS patients from Stockholm, but not from Sassari, also expressed lower (P 〈 0.05) LXR-β (−4.1 ± 0.4) compared to corresponding HC (−2.9 ± 0.3). MS from Stockholm was associated with higher ABCA-1 (6.1 ± 0.4 versus 5.0 ± 0.3; P 〈 0.05) and higher estrogen receptor-β-Cx (2.4 ± 0.4 versus 0.8 ± 0.4; P 〈 0.01) compared to corresponding HC. The HC from Sassari had higher androgen receptor (2.9 ± 0.2) compared to MS from Sassari (1.4 ± 0.3; P 〈 0.01), MS (1.3 ± 0.4; P 〈 0.01) and HC from Stockholm (1.2 ± 0.3; P 〈 0.01). MS from Sassari had lower cyclooxygenase-1 compared to corresponding HC (5.1 ± 0.4 versus 6.6 ± 0.3; P 〈 0.01) and lower prostaglandin-E (−0.03 ± 0.5) compared to the HC (1.4 ± 0.5; P 〈 0.05) and MS (2.7 ± 0.4; P 〈 0.05) and HC from Stockholm (1.9 ± 0.4, P 〈 0.001). Our findings identify LXRs and their related molecules as being involved in MS from Stockholm but not from Sassari, while sex hormone receptors seem to be involved in MS in Sassari.

Electronic Resource

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

IFN-β, an approved drug for multiple sclerosis (MS), acts on dendritic cell (DC) by suppressing their production of IL-12p40 and increasing IL-10. This results in Th2-biased immune responses. The nature of IFN-β-modulated DC remains elusive. Previously, we observed that IFN-β dose dependently induces expression of CD123, i.e. a classical marker for plasmacytoid DC, on human blood monocyte-derived myeloid DC. Such IFN-β-modulated DC produce predominantly IL-10 but are IL-12 deficient, with potent Th2 promotion. In the present study, we further characterize IFN-β-modulated DC by using recently identified blood DC antigens (BDCA) and investigate their ability to produce Type I IFN in response to virus stimulation. We show that IFN-β induces development of CD123+ DC from human blood monocytes, which coexpress BDCA4+ but are negative for BDCA2–, a specific marker for plasmacytoid DC. Such IFN-β-modulated DC produce large amounts of IL-6 and IL-10, but no IL-12p40 and have no enhanced IFN-β and IFN-β production. The findings indicate that IFN-β-modulated DC represent a myeloid DC subset with diminished CD11c, BDCA-1 and CD1a expression, having potent Th2-promoting function but lacking antiviral capacity.

Electronic Resource

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Studies in experimental animal models of human autoimmune diseases have revealed that CD4+CD25+ T regulatory (Tr) cells are of thymic origin and have potentials in preventing auto-aggressive immunity. Myasthenia gravis (MG) is the best-characterized autoimmune disease. Changes in the thymus are found in a majority of patients with MG. Thymectomy has beneficial effects on the disease severity and course in a substantial proportion of MG patients. But the occurrence and characteristics of Tr cells have not yet been defined in MG. We determined the frequencies and properties of circulating CD4+CD25+ versus CD4+CD25– cells in MG patients and healthy controls (HCs), with special focus on the effect of thymectomy on CD4+CD25+ cells. CD4+CD25high cells comprise only about 2% of blood lymphocytes in both MG patients and HCs. Frequencies of CD4+CD25high cells were similar in MG patients irrespective of treatment with thymectomy. CD4+CD25+ cells in both MG patients and HCs are mainly memory T cells and are activated to a greater extent than CD4+CD25– cells, as reflected by high levels of CD45RO and human leucocyte antigen (HLA)-DR-positive cells. In both MG patients and HCs, CD4+CD25+ cells also contained a high proportion of CD95-expressing cells as possible evidence of apoptosis-proneness. Upon stimulation with anti-CD3/CD28 monoclonal antibodies, CD4+CD25+ cells responded more vigorously than CD4+CD25– cells in MG, irrespective of treatment with thymectomy, as well as in HCs. Although CD4+CD25– cells are mainly naïve T cells, in non-thymectomized MG patients, they are activated to a greater extent as reflected by higher expression of HLA-DR and CD95 on the surface compared to HCs. The data thus show that there is no deficiency of CD4+CD25+ cells in MG, nor is the proportion of CD4+CD25+ cells influenced by thymectomy.

Electronic Resource

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Multiple sclerosis (MS) is a disabling, inflammatory, demyelinating disease of the central nervous system considered to be mediated by autoreactive T cells. Dendritic cells (DC), being professional antigen-presenting cells, play a pivotal role in the decision between T-cell activation and anergy. It has been suggested that mature DC (mDC) induce immunity, whereas immature DC (imDC) have the potential to induce tolerance. In this study, we investigated the effects of autologous imDC versus autologous mDC on lymphocytes with respect to the expression of functionally important cell-surface molecules and production of cytokines. Our aims were to investigate whether the maturation status of DC differs between MS and healthy controls (HC) and to explore whether the effects of DC on T-cell responses differ between MS and HC. DC were generated from adherent blood mononuclear cells from patients with MS and HC. imDC were obtained by culture with either granulocyte–macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) or GM-CSF + IL-4 + IL-10. mDC were obtained by adding lipopolysaccharide to DC cultures. Upon coculture with autologous lymphocytes, mDC activated the autologous T cells as reflected by increased CD25 and cytotoxic T-lymphocyte antigen-4 expression on CD4+ T cells together with the increased production of both T helper 1 (Th1) (IL-2 and interferon-γ) and Th2 (IL-10 and IL-4) cytokines. Unmodulated naïve imDC induced the production of only IL-4. An exposure of imDC to IL-10 induced the production of IL-4 as well as IL-10 by autologous lymphocytes. We hypothesize that such imDC are important in controlling the proinflammatory environment in vivo in patients with MS.

Electronic Resource

1432-0630

78.70

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract The effects of uncertainties and errors in various constraints used in the analysis of multi-component life-time spectra of positrons annihilating in metals containing defects have been investigated in detail using computer simulated decay spectra and subsequent analysis. It is found that the errors in the fitted values of the main components lifetimes and intensities introduced from incorrect values of the instrumental resolution function and of the source-surface components can easily exceed the statistical uncertainties. The effect of an incorrect resolution function may be reduced by excluding the peak regions of the spectra from the analysis. The influence of using incorrect source-surface components in the analysis may on the other hand be reduced by including the peak regions of the spectra. A main conclusion of the work is that extreme caution should be exercised to avoid introducing large errors through the constraints used in the analysis of experimental lifetime data.

Electronic Resource

1741-2765

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract This paper combines measured isochromatic information, complex stress functions and numerical concepts into a new and effective hybrid method of stress analysis. The technique simultaneously smooths the measured isochromatic data, provides accurate boundary information, and separates the isochromatic information into normal and shear stresses at nonboundary locations. No additional experimental data such as the isoclinics are needed. The technique is illustrated experimentally by application to a tensile plate containing a hole.

Electronic Resource

1741-2765

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract An effective hybrid method is demonstrated for stress analysis and heat transfer. Measured information is represented and differentiated analytically, while the number of unknown coefficients and amount of experimental input data needed are reduced through field equations. The approach is accurate, full-field, employs arbitrarily shaped elements, does not require a smoothing parameter and is well suited for computer-vision techniques. The concept is presently illustrated by moiré strain analysis, although it can be extended to other disciplines.

Electronic Resource

1741-2765

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract A new thermoelastic hybrid method of stress analysis is demonstrated experimentally which simultaneously smooths the measured isopachic data, enhances the boundary information, and separates the stresses at nonboundary locations using only the isopachics. The technique is illustrated by application to a tensile plate containing a hole.

Electronic Resource

1741-2765

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract Hybrid methods are developed for determining individual stress components under plane stress from thermoelastically measured isopachics. Some of the techniques depend only on stress equilibrium and are independent of constitutive response. Applications are to a partially loaded half-plane, and tensile plates containing side notches and holes. These are believed to represent the first examples of separating stresses from thermoelastically measured data.

Electronic Resource