Sensitivity map of laser tweezers Raman spectroscopy for single-cell analysis of colorectal cancer

Raman spectroscopy on single, living epithelial cells captured in a laser trap is shown to have diagnostic power over colorectal cancer. This new single-cell technology comprises three major components: primary culture processing of human tissue samples to produce single-cell suspensions, Raman detection on singly trapped cells, and diagnoses of the cells by artificial neural network classifications. it is compared with DNA flow cytometry for similarities and differences. Its advantages over tissue Raman spectroscopy are also discussed. In the actual construction of a diagnostic model for colorectal cancer, real patient data were taken to generate a training set of 320 Raman spectra and, a test set of 80. By incorporating outlier corrections to a conventional binary neural classifier, our network accomplished significantly better predictions than logistic regressions, with sensitivity improved from 77.5% to 86.3% and specificity improved from 81.3% to 86.3% for the training set and moderate improvements for the test set. Most important, the network approach enables a sensitivity map analysis to quantitate the relevance of each Raman band to the normal-to-cancer transform at the cell level. Our technique has direct clinic applications for diagnosing cancers and basic science potential in the study of cell dynamics of carcinogenesis. (C) 2007 Society of Photo-Optical Instrumentation Engineers.

Study of the effect of alcohol on single human red blood cells using near-infrared laser tweezers Raman spectroscopy

The effect of alcohol solution on single human red blood Cells (RBCs) was investigated using near-infrared laser tweezers Raman spectroscopy (LTRS). In our system, a low-power diode laser at 785 nm was applied for the trapping of a living cell and the excitation of its Raman spectrum. Such a design could simultaneously reduce the photo-damage to the cell and suppress the interference from the fluorescence on the Raman signal. The denaturation process of single RBCs in 20% alcohol solution was investigated by detecting the time evolution of the Raman spectra at the single-cell level. The vitality of RBCs was characterized by the Raman band at 752 cm(-1), which corresponds to the porphyrin breathing mode. We found that the intensity of this band decreased by 34.1% over a period of 25 min after the administration of alcohol. In a further study of the dependence of denaturation on alcohol concentration, we discovered that the decrease in the intensity of the 752 cm(-1) band became more rapid and more prominent as the alcohol concentration increased. The present LTRS technique may have several potential applications in cell biology and medicine, including probing dynamic cellular processes at the single cell level and diagnosing cell disorders in real time. Copyright (c) 2005 John Wiley T Sons, Ltd.

Diagnosis of colorectal cancer using Raman spectroscopy of laser-trapped single living epithelial cells

A single-cell diagnostic technique for epithelial cancers is developed by utilizing laser trapping and Raman spectroscopy to differentiate cancerous and normal epithelial cells. Single-cell suspensions were prepared from surgically removed human colorectal tissues following standard primary culture protocols and examined in a near-infrared laser-trapping Raman spectroscopy system, where living epithelial cells were investigated one by one. A diagnostic model was built on the spectral data obtained from 8 patients and validated by the data from 2 new patients. Our technique has potential applications from epithelial cancer diagnosis to the study of cell dynamics of carcinogenesis. (c) 2006 Optical Society of America.

Sensitivity map of laser tweezers Raman spectroscopy for single-cell analysis of colorectal cancer

Raman spectroscopy on single, living epithelial cells captured in a laser trap is shown to have diagnostic power over colorectal cancer. This new single-cell technology comprises three major components: primary culture processing of human tissue samples to produce single-cell suspensions, Raman detection on singly trapped cells, and diagnoses of the cells by artificial neural network classifications. it is compared with DNA flow cytometry for similarities and differences. Its advantages over tissue Raman spectroscopy are also discussed. In the actual construction of a diagnostic model for colorectal cancer, real patient data were taken to generate a training set of 320 Raman spectra and, a test set of 80. By incorporating outlier corrections to a conventional binary neural classifier, our network accomplished significantly better predictions than logistic regressions, with sensitivity improved from 77.5% to 86.3% and specificity improved from 81.3% to 86.3% for the training set and moderate improvements for the test set. Most important, the network approach enables a sensitivity map analysis to quantitate the relevance of each Raman band to the normal-to-cancer transform at the cell level. Our technique has direct clinic applications for diagnosing cancers and basic science potential in the study of cell dynamics of carcinogenesis. (C) 2007 Society of Photo-Optical Instrumentation Engineers.

Optical spectroscopy of Yb3Al5O12 single crystal

Yb3Al5O12 single crystal has been grown by Czochralski (CZ) method. The absorption spectrum was investigated at low temperature and the electronic energy levels for F-2(5/2) multiplet of Yb3+ in YbAG was proposed. The up-conversion emission of the crystal under 940 nm diode pumping and the X-ray excited luminescence (XEL) features of the crystal were also studied. (c) 2005 Elsevier B.V. All rights reserved.

A NOVEL PLASMINOGEN-ACTIVATOR FROM SNAKE-VENOM - PURIFICATION, CHARACTERIZATION, AND MOLECULAR-CLONING

A novel plasminogen activator from Trimeresurus stejnegeri venom (TSV-PA) has been identified and purified to homogeneity. It is a single chain glycoprotein with an apparent molecular weight of 33,000 and an isoelectric point of pH 5.2. It specifically activates plasminogen through an enzymatic reaction. The activation of human native GIu-plasminogen by TSV-PA is due to a single cleavage of the molecule at the peptide bond Arg(561)-Val-(562). Purified TSV-PA, which catalyzes the hydrolysis of several tripeptide p-nitroanilide substrates, does not activate nor degrade prothrombin, factor X, or protein C and does not clot fibrinogen nor show fibrino(geno)lytic activity in the absence of plasminogen. The activity of TSV-PA was readily inhibited by phenylmethanesulfonyl fluoride and by p-nitrophenyl-p-guanidinobenzoate. Oligonucleotide primers designed on the basis of the N-terminal and the internal peptide sequences of TSV-PA were used for the amplification of cDNA fragments by polymerase chain reaction. This allowed the cloning of a full-length cDNA encoding TSV-PA from a cDNA library prepared from the venom glands. The deduced complete amino acid sequence of TSV-PA indicates that the mature TSV-PA protein is composed of 234 amino acids and contains a single potential N-gIycosylation site at Asn(1G1). The sequence of TSV-PA exhibits a high degree of sequence identity with other snake venom proteases: 66% with the protein C activator from Aghistrodon contortrix contortrix venom, 63% with batroxobin, and 60% with the factor V activator from Russell's viper venom. On the other hand, TSV-PA shows only 21-23% sequence similarity with the catalytic domains of u-PA and t-PA. Furthermore, TSV-PA lacks the sequence site that has been demonstrated to be responsible for the interaction of t-PA (KHRR) and u-PA (RRHR) with plasminogen activator inhibitor type 1.

Controlling electronic structures by irradiation in single-walled SiC nanotubes: a first-principles molecular dynamics study

Using first-principles molecular dynamics simulations, the displacement threshold energy and defect configurations are determined in SiC nanotubes. The simulation results reveal that a rich variety of defect structures (vacancies, Stone-Wales defects and antisite defects) are formed with threshold energies from 11 to 64 eV. The threshold energy shows an anisotropic behavior and exhibits a dramatic decrease with decreasing tube diameter. The electronic structure can be altered by the defects formed by irradiation, which suggests that the electron irradiation may be a way to use defect engineering to tailor electronic properties of SiC nanotubes.

GaAs-based room-temperature continuous-wave 1.59 mu m GaInNAsSb single-quantum-well laser diode grown by molecular-beam epitaxy

Starting from the growth of high-quality 1.3 mu m GaInNAs/GaAs quantum well (QW), the QW emission wavelength has been extended up to 1.55 mu m by a combination of lowering growth rate, using GaNAs barriers and incorporating some amount of Sb. The photoluminescence properties of 1.5 mu m range GaInNAsSb/GaNAs QWs are quite comparable to the 1.3 mu m QWs, revealing positive effect of Sb on improving the optical quality of the QWs. A 1.59 mu m lasing of a GaInNAsSb/GaNAs single-QW laser diode is obtained under continuous current injection at room temperature. The threshold current density is 2.6 kA/cm(2) with as-cleaved facet mirrors. (c) 2005 American Institute of Physics.

Surface-enhanced resonant Raman spectroscopy (SERRS) of single-walled carbon nanotubes absorbed on the Ag-coated anodic aluminum oxide (AAO) surface

In this paper, we developed a new kind of substrate, the silver-coated anodic aluminum oxide (AAO), to investigate the characters of surface-enhanced resonant Raman scattering (SERRS) of the dilute single-walled carbon nanotubes. Homogeneous Ag-coated AAO substrate was obtained by decomposing the AgNO3 on the surface of AAO. single-walled carbon nanotubes (SWNTs) were directly grown onto this substrate through floating catalyst chemical vapor deposition method (CVD). SERRS of SWNTs was carried out using several different wavelength lasers. The bands coming from metallic SWNTs were significantly enhanced. The two SERRS mechanisms, the "electromagnetic" and "chemical" mechanism, were mainly responsible for the experiment results. (c) 2005 Elsevier B.V. All rights reserved.

Study of GaN thin films grown on intermediate-temperature buffer layers by molecular beam epitaxy

A detailed characterisation study of GaN thin films grown by rf-plasma molecular beam epitaxy on intermediate-temperature buffer layers (ITBL) was carried out with Hall, photoluminescence (PL) and deep-level transient Fourier spectroscopy (DLTFS) techniques. The unique feature of our GaN thin films is that the GaN epitaxial layers are grown on top of a double layer that consists of an ITBL, which is grown at 690 degreesC, and a conventional low-temperature buffer layer deposited at 500 degreesC. It is observed that the electron mobility increases steadily with the thickness of the ITBL, which peaks at 377 cm(2)V(-1)S(-1) for an ITBL thickness of 800 nm. The PL also demonstrated systematic improvements with the thickness of the ITBL. The DLTFS results suggest a three-order-of-magnitude reduction in the deep level at E-c-0.40 eV in the device fabricated with the GaN films grown on an ITBL thickness of 1.25 mum in comparison with the control device without an ITBL. Our analyses indicate that the utilization of an ITBL in addition to the conventional low-temperature buffer layer leads to the relaxation of residual strain within the material, resulting in an improvement in the optoelectronic properties of the films. (C) 2002 Elsevier Science BN. All rights reserved.

High-temperature characteristics of GaInNAs/GaAs single-quantum-well lasers grown by plasma-assisted molecular beam epitaxy

GaInNAs/GaAs single-quantum-well (SQW) lasers have been grown by solid-source molecular beam epitaxy. N is introduced by a home-made de-active plasma source. Incorporation of N into InGaAs decreases the bandgap significantly. The highest N concentration of 2.6% in a GaInNAs/GaAs QW is obtained, corresponding to the photoluminescence (PL) peak wavelength of 1.57 mum at 10 K. The PL peak intensity decreases rapidly and the PL full width at half maximum increases with the increasing N concentrations. Rapid thermal annealing at 850 degrees C could significantly improve the crystal quality of the QWs. An optimum annealing time of 5s at 850 degrees C was obtained. The GalnNAs/GaAs SQW laser emitting at 1.2 mum exhibits a high characteristic temperature of 115 K in the temperature range of 20 degrees C- 75 degrees C.

Effects of rapid thermal annealing and SiO2 encapsulation on GaNAs/GaAs single quantum wells grown by plasma-assisted molecular-beam epitaxy

Effects of rapid thermal annealing and SiO2 encapsulation on GaNAs/GaAs single quantum wells grown by plasma-assisted molecular-beam epitaxy were studied. Photoluminescence measurements on a series of samples with different well widths and N compositions were used to evaluate the effects. The intermixing of GaNAs and GaAs layers was clearly enhanced by the presence of a SiO2-cap layer. However, it was strongly dependent on the N composition. After annealing at 900 degreesC for 30 s, a blueshift up to 62 meV was observed for the SiO2-capped region of the sample with N composition of 1.5%, whereas only a small blueshift of 26 meV was exhibited for the bare region. For the sample with the N composition of 3.1%, nearly identical photoluminescence peak energy shift for both the SiO2-capped region and the bare region was observed. It is suggested that the enhanced intermixing is mainly dominated by SiO2-capped layer induced defects-assisted diffusion for the sample with smaller N composition, while with increasing N composition, the diffusion assisted by interior defects become predominant. (C) 2001 American Institute of Physics.

Effects of rapid thermal annealing on the optical properties of GaNxAs1-x/GaAs single quantum well structure grown by molecular beam epitaxy

The effect of rapid thermal annealing (RTA) on the optical properties of GaNxAs1-x/GaAs strained single quantum well (SQW) was studied by low-temperature photoluminescence (PL). The GaNxAs1-x/GaAs SQW structures were prepared by dc active nitrogen plasma assisted molecular beam epitaxy. PL measurements on a series of samples with different well widths and nitrogen compositions were used to evaluate the effects of RTA. The annealing temperature and time were varied from 650 to 850 degrees C and 30 s to 15 min, respectively. Remarkable improvements of the optical properties of the samples were observed after RTA under optimum conditions. The interdiffusion constants have been calculated by taking into account error function diffusion and solving the Schrodinger equation. The estimated interdiffusion constants D are 10(-17)-10(-16) cm(2)/s for the earlier annealing conditions. Activation energies of 6-7 eV are obtained by fitting the temperature dependence of the interdiffusion constants. (C) 2000 American Institute of Physics. [S0021-8979(00)10401-3].

Structural characterization of SiGe/Si single wells grown by disilane and solid-Ge molecular beam epitaxy with varied disilane cracking temperature

Structural properties of SiGe/Si single wells are studied by double-crystal X-ray diffraction. Four SiGe/Si single wells have been grown on Si (0 0 1) at 750 degrees C by disilane and solid-Ge molecular beam epitaxy with varied disilane cracking temperature. Using dynamic theory, together with kinematic theory and the specific growth procedure adopted, structural parameters in the multilayer structure are determined precisely. The results are compared with those obtained from PL and XTEM as well as AES measurements. It is found that disilane adsorption is dependent on cracking temperature as well as Ge incorporation. Disilane adsorption is increased by cracking disilane while it decreased with Ge incorporation (C) 1998 Elsevier Science B.V. All rights reserved.

Conduction-band offset in a pseudomorphic GaAs/In0.2Ga0.8As quantum well determined by capacitance-voltage profiling and deep-level transient spectroscopy techniques

The conduction-band offset Delta E-C has been determined for a molecular beam epitaxy grown GaAs/In0.2Ga0.8As single quantum-well structure, by measuring the capacitance-voltage (C - V) profiling, taking into account a correction for the interface charge density, and the capacitance transient resulting from thermal emission of carriers from the quantum well, respectively. We found that Delta E-C = 0.227 eV, corresponding to about 89% Delta E-g, from the C - V profiling; and Delta E-C = 0.229eV, corresponding to about 89.9% Delta E-g, from the deep-level transient spectroscopy (DLTS) technique. The results suggest that the conduction-band discontinuity Delta E-C obtained from the C-V profiling is in good agreement with that obtained from the DLTS technique. (C) 1998 American Institute of Physics.