Monitoring microarray-based gene expression profile changes in hepatocellular carcinoma

AIM: To find out key genes responsible for hepatocarc inogenesis and to further understand the underlying molecular mechanism through investigating the differential gene expression between human normal liver tissue and hepatocellular carcinoma (HCC).METHODS: DNA microarray was prepared by spotting PCR products of 1 000 human genes including 445 novel genes, 540 known genes as well as 12 positive (housekeeping) and 3 negative controls (plant gene) onto treated glass slides. cDNA probes were prepared by labeling normal liver tissue mRNA and cancer liver tissue mRNA with Cy3-dUTP and Cy5-dUTP separately through reverse transcription. The arrays were hybridized against the cDNA probe and the fluorescent signals were scanned. The dataobtained from repeated experiments were analyzed. RESULTS: Among the 20 couple samples investigated (from cancerous liver tissue and normal liver tissue), 38 genes including 21 novel genes and 17 known genes exhibited different expressions. CONCLUSION: cDNA microarray technique is powerful to identify candidate target genes that may play important roles in human carcinogenesis. Further analysis of the obtained genes is helpful to understand the molecular changes in HCC progression and ultimately may lead to the identification of new targets for HCC diagnosis and intervention.

An Emphasis of Electron Energy Calculation in Quantum Wells

We investigate various methods for the calculation of the electron energy in semiconductor quantum wellsand focus on a matrix algorithm method. The results show better fitness of the factor -h/2 / z 1/m* (z) / z than that ofh2/2 1/m*(z) 2/ z2in the first part of the Schrodinger equation. The effect of nonparabolicity in the conduction band isalso discussed.

Microstructural and Electrical Properties of ZrO2 Thin Films prepared on Silicon on Insulator with Thin Top silicon

Amorphous zirconia thin films were deposited directly on silicon-on-insulator(SOI) substrates with this top silicon by ultra-high vacuum electron beam evaporation.Spearding resistance profile and scanning transmission-electron microscopy(TEM) were used to detect the interface quality and microstructure,revealing that the interface between the zirconium oxide films and top silicon was abrupt and clear.The films kept to be amorphous up to the rapid thermal temperature of 700℃for 300s，but arriving at 700℃an unknown interfacial product appeared,which was probably ZrSixOy.High frequency cacacitance-voltage(C-V) characteristics at 1MHz performed on metal-oxide-SOI structure revealed that this interfacial product exhibited good electrical properties of zirconia thin films.When the annealing temperature increased from 600℃to 700℃,flat voltage VFB changed from -2.451to-1.741eV,showing the improvement in the quality of the films,The cumulative region capacitance decreased from 3.058×10^-11 F to 3.012×10^-11F,indicating increasing equivalent oxide thickness,which is in agreement with the result of high-resolution cross-sectional TEM>

Numerical Analysis of Multilayer Waveguides Using Effective Refractive Index Method

With the help of the effective refractive index method we have numerically analyzed a multilayer planar waveguide structure and calculated the propagation constants, confinement factors, and transverse electric (TE) modes. A five-layer waveguide model has been provided to analyze the electro-magne tic wave propagation process. The analysis method has been applied to the 980 nm laser with active layer of GaInAs/GaInAsP strained quantum wells, GaInAsP confinement layers and GaInP cap layers. By changing the thickness of confinement layers, we obtained confinement factor as high as 95% with higher TE modes TE1 and TE2. The results are in good agreement with the experiment by A. Al-Muhanna et al. and give the new idea to enhance output power of semiconductor lasers. The analysis method can also be extended to any other slab multilayer waveguide structures, and the results are useful to the fabrication of optic-electronic devices.

Transient Intersubband Optical Absorption in Double Quantum Well Structure

The microscopic equations of motion including many-body effects are derived to study the intersubband polarization in the double quantum well structure induced by an ultrafast pumping infrared light. Based on the selfconsistent field theory, the transient probe absorption coefficient is calculated. These calculations are beyond the previous steady-state assumption. Transient probe absorption spectra are calculated under different pumping intensity and various pump probe delay.

Length reduction factor of tapered multimode interference devices

Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices based on weakly- restricted waveguide. Based on the analysis with mode width as a substitution of waveguide width, a design formula with better precision was presented. Comparison with software simulation verified its exactness.

A Direct Parameter-Extraction Method for GaInP/GaAs Heterojunction Bipolar Transistors Small-Signal Model

An accurate and broad-band method for hetero-junction bipolar transistors(HBT) small-signal model parameters-extraction is presented in this paper. An equivalent circuit forthe HBT under a forward-bias condition is proposed for extraction of accessresistance and parasiticinductance. This method differs from previous ones by extracting the c-quivalent circuit parameterswithout using special test structure or global numerical optimization techniques. The mainadvantage of this method is that a unique and physically meaningful set of intrinsic parameters isextracted from impedance and admittance representation of the measured S-pa-rameters in thefrequency range of 1-12 GHz under different bias conditions. The method yields a deviation of lessthan 5% between measured and modeled S-parameters.