Search results

1

The role of B lymphocytes as antigen-presenting cells

100%

Chen X., Jensen P. E.

Archivum Immunologiae et Therapiae Experimentalis

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2008

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vol. 56

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issue 2

77-83

EN

B lymphocytes are regarded as professional antigen-presenting cells (APCs) despite their primary role in humoral immunity. Over the last two decades, studies designed to define the role of the B cells as APCs have generated discrepant results, showing that B cells are either unnecessary or required for T cell priming and either immunogenic or tolerogenic to T cells. The reasons for these discrepancies are not clear. Here we review mechanisms regulating B cell antigen presentation and the data derived from the major studies conducted by different groups representing each school of thought. In general it is clear that B cells process and present specific and nonspecific antigens differently. The presentation of specific antigen through the B cell antigen receptor occurs with very high efficiency and is associated with B cell activation, resulting in the activation of cognate T cells. In contrast, the presentation of nonspecific antigen by B cells is minimized and dissociated from B cell activation. As a result, B cells inactivate T cells that recognize nonspecific antigenic epitopes presented by B cells, or they induce regulatory T cell differentiation or expansion. These mechanisms serve to ensure effective production of high-affinity antigen-specific antibodies but minimize the production of nonspecific antibodies and autoantibodies.

2

Nonlinear damage accumulation of concrete subjected to variable amplitude fatigue loading

81%

Chen Y., Chen X., Bu J.

Bulletin of the Polish Academy of Sciences: Technical Sciences

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2018

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issue 2

3

High Speed Heterostructure Metal-Semiconductor-Metal Photodetectors

81%

Cola A., Nabet B., Chen X., Quaranta F.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

14-25

EN

In this work we review the properties of a class of metal-semiconductor-metal photodetectors based on heterojunction structures. Particularly, an AlGaAs/GaAs device is detailed in which the absorption region is in the GaAs layer, and a two-dimensional electron gas is formed at the heterointerface due toδ-doping of the widegap material. This heterostructure metal-semiconductor-metal photodetector also contains an AlGaAs distributed Bragg reflector that forms a resonant cavity for detection at 850 nm. The beneficial effect of the two-dimensional electron gas in the GaAs absorption layer in terms of speed and sensitivity is demonstrated by comparing samples with and without doping in the AlGaAs layer. The design and the physical properties of the grown epitaxial structure are presented, together with the static and dynamic characteristics of the device in time domain. In particular, photocurrent spectra exhibit a 30 nm wide peak at 850 nm, and time response measurements give a bandwidth over 30 GHz. A combination of very low dark current and capacitance, fast response, wavelength selectivity, and compatibility with high electron mobility transistors makes this device suitable for a number of application areas, such as Gigabit and 10 Gigabit Ethernet, wavelength division multiplexing, remote sensing, and medical applications.

4

Thermodynamic and Electronic Properties of OsB_2 from First-Principles Calculations

71%

Cheng Y., Yang J., Wang Y., Ji G., Chen X.

Acta Physica Polonica A

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2014

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vol. 125

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issue 5

1186-1190

EN

The pressure induced phase transitions of OsB_2 from the orthorhombic structure (Orth) to the hexagonal structure (Hex) is investigated by using ab initio plane-wave pseudopotential density functional theory, together with quasi-harmonic Debye model. We find that the pressure-induced phase transition occurs at 2.8 GPa and 12.5 GPa by local density approximation and general gradient approximation, respectively. It is predicted that OsB_2 has no phase transition temperature from the Orth structure to the Hex structure. Moreover, the dependences of the relative volume V/V_0 on the pressure, thermal expansion coefficient α on the pressure and temperature are also successfully obtained. The electronic properties including energy band, total and partial density of states and electron density difference for two structures are also analyzed. The Mulliken charges and Bond populations for both Orth and Hex structures are also obtained.

5

Elastic and Thermodynamic Properties of Anti-Perovskite Type Superconductor MCNi_3 (M = Zn, Cd)

71%

Duan M., Tan J., Ji G., Chen X., Zhu J.

Acta Physica Polonica A

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2010

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vol. 118

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issue 4

652-658

EN

The elastic and thermodynamic properties of the anti-perovskite superconductor ZnCNi_3 and CdCNi_3 are investigated by first-principles calculations. With the local density approximation as well as the generalized gradient approximation for exchange and correlation, the ground state properties and equation of state are obtained, which agree well with other theoretical calculations and experiments. Furthermore, by the elastic stability criteria, we predict that ZnCNi_3 and CdCNi_3 are not stable above 98.1 GPa and 196.5 GPa, respectively. The dependences of the heat capacity, thermal expansion coefficient, the Grüneisen parameter and bulk modulus (B_{T} and B_{S}) on pressure and temperature for ZnCNi_3 and CdCNi_3 are also obtained successfully.

6

Electron Transport and Microwave Noise in MBE- and MOCVD-Grown AlGaN/AlN/GaN

61%

Matulionis A., Liberis J., Eastman L., Schaff W., Shealy J., Chen X., Sun Y.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

361-364

EN

Microwave noise temperature, current, and dissipated power were investigated at room temperature in undoped AlGaN/AlN/GaN channels grown by molecular beam epitaxy and metal-organic compound vapour decomposition techniques. Samples with essentially the same electron density (1×10^{13} cm^{-2}) and low-field mobility (1150 cm^2/(V s)) demonstrated considerably different behaviour at high electric fields. The effective hot-phonon lifetime, 300 fs and 1000 fs, respectively, was estimated for molecular beam epitaxy and metal-organic compound vapour decomposition samples. The expected anti-correlation of hot-phonon lifetime and hot-electron drift velocity was confirmed experimentally.

7

Acquisition of the Surface Morphology of Ruled Gratings with a Microscope Objective

61%

Li Z., Ma L., Liu C., Zhang M., Chen X., Cheng C.

Acta Physica Polonica A

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2015

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vol. 127

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issue 6

1630-1634

EN

In this paper, an optical microscope objective with large numerical number is inserted into a Mach-Zehnder interferometer, and this system is adopted to detect the surface morphologies of two ruled transmission gratings with area scale to a micrometer. The object waves transmitting from the gratings interfere with spherical reference wave, and the interferograms constructed are recorded by a high-resolution CCD. The surface maps of the gratings are retrieved from the interferograms, and the results are confirmed by the measurement with an atomic force microscope, with detection errors in nanometer scale. This work provides an optical non-destructive method for precise detection of small-area sophisticated object surfaces with an optical microscope objective.

8

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

52%

Cieplak M., Adamus Z., Konczykowski M., Chen X., Byczuk A., Abal'oshev A., Sang H., Chien C.

Acta Physica Polonica A

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2004

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vol. 106

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issue 5

693-698

EN

The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model.

9

Telomerase enhances osteogenic ifferentiation of sheep bone marrow mesenchymal stem cells (BMSCs) by up-regulating PI3K/Akt pathway in vitro

45%

Zhu X., Zhou L., Liu Z., Chen X., Wei L., Zhang Z., Liu Y., Zhu Y., Wang Y., Yang X., Han Y., Zhu X., Zhou L., Liu Z., Chen X., Wei L., Zhang Z., Liu Y., Zhu Y., Wang Y., Yang X., Han Y.

Polish Journal of Veterinary Sciences

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2020

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vol. 23

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issue 3

Refine search results

The role of B lymphocytes as antigen-presenting cells

Nonlinear damage accumulation of concrete subjected to variable amplitude fatigue loading

High Speed Heterostructure Metal-Semiconductor-Metal Photodetectors

Thermodynamic and Electronic Properties of OsB_2 from First-Principles Calculations

Elastic and Thermodynamic Properties of Anti-Perovskite Type Superconductor MCNi_3 (M = Zn, Cd)

Electron Transport and Microwave Noise in MBE- and MOCVD-Grown AlGaN/AlN/GaN

Acquisition of the Surface Morphology of Ruled Gratings with a Microscope Objective

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

Telomerase enhances osteogenic ifferentiation of sheep bone marrow mesenchymal stem cells (BMSCs) by up-regulating PI3K/Akt pathway in vitro