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The NCBI Reference Sequence (RefSeq) project and the NIH Mammalian Gene Collection (MGC) together define a set of similar to30,000 nonredundant human mRNA sequences with identified coding regions representing 17,000 distinct loci. These high-quality mRNA sequences allow for the identification of transcribed regions in the human genome sequence, and many researchers accept them as the correct representation of each defined gene sequence. Computational comparison of these mRNA sequences and the recently published essentially finished human genome sequence reveals several thousand undocumented nonsynonymous substitution and frame shift discrepancies between the two resources. Additional analysis is undertaken to verify that the euchromatic human genome is sufficiently complete-containing nearly the whole mRNA collection, thus allowing for a comprehensive analysis to be undertaken. Many of the discrepancies will prove to be genuine polymorphisms in the human population, somatic cell genomic variants, or examples of RNA editing. It is observed that the genome sequence variant has significant additional support from other mRNAs and ESTs, almost four times more often than does the mRNA variant, suggesting that the genome sequence is more accurate. In similar to15% of these cases, there is substantial support for both variants, suggestive of an undocumented polymorphism. An initial screening against a 24-individual genomic DNA diversity panel verified 60% of a small set of potential single nucleotide polymorphisms from which successful results could be obtained. We also find statistical evidence that a few of these discrepancies are due to RNA editing. Overall, these results suggest that the mRNA collections may contain a substantial number of errors. For current and future mRNA collections, it may be prudent to fully reconcile each genome sequence discrepancy, classifying each as a polymorphism, site of RNA editing or somatic cell variation, or genome sequence error.

Picric acid is a dangerous environmental pollutant due to its high toxicity, and the detection of picric acid in the environment is of great significance. The Cd2+ on the surface of CdS crystals can enrich negative ionic compound to form a complex in water. Therefore, the micro CdS crystals have been synthesised using thioacetamide and cadmium sulfate by means of a simple and cheap hydrothermal method for the detection of picric acid and were characterised by means of X-ray diffractometer, scanning electron microscopy, energy-dispersive spectrometer and AC impedance technique. The electrochemical reduction of picric acid at micro CdS crystal-modified glassy carbon electrode was investigated, revealing that the micro CdS crystals could catalyze picric acid, and the reduction mechanism of picric acid on the surface of micro CdS crystals was also discussed. Based on the reduction of picric acid at the modified electrode, a simple method of detection for picric acid was proposed by applying voltammetry, and a linear regression equation was obtained as I (10−5A) = 6160.53279 c (mol.L−1) + 2.51034 (R = 0.9997) with a recoveries of 96.0–101.0% and relative standard deviations of 1.3–2.9% (n = 6), confirming very high sensitivity and selective detection of picric acid at the micro CdS crystal-modified glassy carbon electrode. [ABSTRACT FROM AUTHOR]

Photoreflectance is used to investigate the band gap, built-in electric field, and surface Fermi level of a series of lattice-matched In[sub 0.52]Al[sub 0.48]As surface-intrinsic n[sup +] structures having different undoped layer thicknesses. Experimental results indicate that, although the built-in electric field depends on the undoped layer thickness, there is a range of thickness within which the surface Fermi level is weakly pinned. From the dependence of electric field and surface Fermi level on the undoped layer thickness, we can determine that the surface states distribute over two separate regions within the energy band gap. The densities of the surface states are evaluated as well. Moreover, the dependence of the built-in electric field on undoped layer thickness is converted into the dependence of surface state density on the surface Fermi level in order to theoretically and exactly calculate the energy spectrum of the surface state density using a Guassian distribution function. The center and width of the distribution near the conduction band are obtained from the fitting parameters. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the effects of elastic strain induced by lattice mismatch on the effective mass and band offset at T point of indium gallium antimonide. Methods; Results; Discussion.

Both the epitaxial-strain and atomic-ordering effects in In0.54Ga0.46P1-yNy/GaAs (y=0%-2.0%) heterostructures are characterized by high-resolution x-ray rocking curve measurements and photoreflectance (PR) spectra at various temperatures. The lattice constant of InGaPN follows a bowing effect instead of Vegard’s law. The valence-band splitting (VBS) and spin-orbit splitting of InGaPN are obtained from PR spectra. As the nitrogen concentration increases, the lattice mismatch (the compressive strain) between the epilayer and GaAs substrate decreases while the VBS increases, which implies an increase in the degree of ordering of InGaPN. In addition, the order parameter η of InGaPN is deduced from the VBS. [ABSTRACT FROM AUTHOR]

The electroreflectance (ER) spectra of a surface-intrinsic n[sup +]-type doped (100) GaAs have been measured at various polarization angles of the probe beam. Several Franz–Keldysh oscillations were observed above the band-gap energy, thus enabling heavy- and light-hole transitions to be separated by the application of the fast Fourier transform to the ER spectra. From this, the ratios of the amplitudes of the light- to heavy-hole transitions versus angle of polarization were obtained. At a large incident angle (80°), the strength of the field of the probe beam in the normal direction of the sample (F[sub z]) was varied from zero to a larger component. It was found that the ratios increased with increasing F[sub z] which is consistent with the theory that the light-hole transition becomes more enhanced with z-polarized light. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]