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Modified kernel-based nonlinear feature extraction.

Description: Feature Extraction (FE) techniques are widely used in many applications to pre-process data in order to reduce the complexity of subsequent processes. A group of Kernel-based nonlinear FE ( H E ) algorithms has attracted much attention due to their high performance. However, a serious limitation that is inherent in these algorithms -- the maximal number of features extracted by them is limited by the number of classes involved -- dramatically degrades their flexibility. Here we propose a modified version of those KFE algorithms (MKFE), This algorithm is developed from a special form of scatter-matrix, whose rank is not determined by the number of classes involved, and thus breaks the inherent limitation in those KFE algorithms. Experimental results suggest that MKFE algorithm is .especially useful when the training set is small.
Date: January 1, 2002
Creator: Ma, J. (Junshui); Perkins, S. J. (Simon J.); Theiler, J. P. (James P.) & Ahalt, S. (Stanley)
Partner: UNT Libraries Government Documents Department

Conformational Diversity in (Octaethylporphinato) (trichloroacetato)iron(III) Derivatives

Description: Treatment of [Fe(OEP)]20 with trichloroacetic acid results in ruffled formation of (octaethylporphinato trichloroacetato)iron(HI). Various crystalline solvates can be isolated, depending on the crystallization solvent. Initial crystallization with CHC13/hexanes resulted in the isolation of an unsolvated form. [Fe(OEP)(02C2C13 )]. This form contains distinct porphyrin core conformations at the same site: one is domed and the other is ruffled. Crystal data for [Fe(OEP)(02C2C13 )]: Q = 14.734(4) .4. b = 13.674(1) .\. c = 17..541 [,.5] .~. 3 = 90.67(1)0, V = 35-!5.8(14) .\3. monoclinic. space group R1/ n. Z = 4. Subsequent crystallization with CHC13/hexanes resulted in a new crystalline form, [Fe(OEP)(OzC2C13 )~.- CHC13; the porphyrin core is slightly ruffled. Crystal data for [Fe(OEP)(OoC2C13 )]. CHC13: a =12.323(1) .~, 6 = 13.062(3) .\. C = 14.327(2) .$, Q = 89.32(1)", .3 = 113.36(2)0. :~ = 105.26(1)'. V = `2031.3(6) .\3. triclinic. space group Pi. Z = 2. Crystallization with CH2C12/hexanes resulted in the isolation of yet another form, [Fe(OEP) (02 C2C13)]. H02C2C13. which contains two independent molecules in the unit cell: molecule is slightly saddled and molecule B is modestly ruffled. Crystal data for [Fe(OEP)(02ClC13 )]. H02C2C13: a = 13.148(3) .\, b = 13.45.5(3) A, c = Q3.761(5) -& ~ = 90.72(3)", ~ = 91. ~4(3)". -y = 92.36(3)0, V = 4198.5(15) .\3, triclinic.space group PI, Z = 4. .+11 conformations form dimers in the solid state. Temperature-dependent manometic susceptibility measurements showed that [Fe(OEP)(02C2C13)] .CHC13 contains a high-spin iron(III) center; the data for {Fe(OEP)(02C2C13 )l.H02C2C13 are understood in terms of an admixed intermediate-spin state (S = 3/2, 5/2) and are readily fit to a faltempo model with a ground state multiplet containing about 78% S = 5/2 character and 22% S = 3/2 character. The structural data for [Fe(OEP)(02C2C13 )]. CHC13 are consistent with the observed high-spin state, while data for ...
Date: October 19, 1998
Creator: Cheng, B.; Ma, J.; Neal, T.J.; Scheidt, W.R.; Schulz, C.E. & Shelnutt, J.A.
Partner: UNT Libraries Government Documents Department

Toxicity studies of mild gasification products

Description: The objectives of this project are: (1) to perform mutagenicity studies with the Ames Salmonella/microsomal assay system on coal liquids produced by mild gasification from different coals and/or processing conditions, (2) to determine whether coal liquids which are mutagenic to bacteria are also genotoxic to mammalian cells, (3) to establish correlations between mutagenicity, aromaticity, and boiling point range of coal liquids, and (4) to identify the chemical classes which are likely to be responsible for the mutagenic activity of gasification products. Four of the seven samples tested so far failed to demonstrate any mutagenic activity under any conditions tested. Those samples were SHELL[number sign]830331, MG-122IBP-420[degree]F, MG-122 420--720[degree]F, and MG-122 720[degree]F+. Table 1 summarizes the results from all samples tested in DMSO and Tween 80. When solvated in DMSO, MG-119 and MG-120 composite materials displayed slight, but ultimately insignificant, genotoxic activity on TA98 and TA1OO in the presence of S9. When Tween 80 was used as the solvent, MG-119 and MG-120 displayed slight, but significant, geno-toxic activity on TA98 with S9 (Figure 4). CTC[number sign]11 in DMSO displayed significant genotoxic activity on both TA98 and TA1OO with and without S9. The activity was higher on TA98 than TA100, and higher with S9 than without, primarily indicating the presence of indirect-acting frameshift mutagen. The results of the testing on CTC[number sign]11 were similar for both solvents, DMSO and Tween 80 (Table 2).
Date: January 1, 1992
Creator: Ong, T.M.; Whong, W.Z.; Ma, J.; Zhong, B.Z. & Bryant, D.
Partner: UNT Libraries Government Documents Department

The Quantum Mixed-Spin Heme State of Barley Peroxidase: A Paradigm for Class III Peroxidases

Description: Electronic absorption and resonance Raman (RR) spectra of the ferric form of barley grain peroxidase (BP 1) at various pH values both at room temperature and 20 K are . reported, together with EPR spectra at 10 K. The ferrous forms and the ferric complex with fluoride have also been studied. A quantum mechanically mixed-spin (QS) state has been identified. The QS heme species co-exists with 6- and 5-cHS heroes; the relative populations of these three spin states are found to be dependent on pH and temperature. However, the QS species remains in all cases the dominant heme spin species. Barley peroxidase appears to be further characterized by a splitting of the two vinyl stretching modes, indicating that the vinyl groups are differently conjugated with the porphyrin. An analysis of the presently available spectroscopic data for proteins from all three peroxidase classes suggests that the simultaneous occurrence of the QS heme state as well as the splitting of the two vinyl stretching modes is confined to class III enzymes. The former point is discussed in terms of the possible influences of heme deformations on heme spin state. It is found that moderate saddling alone is probably not enough to cause the QS state, although some saddling maybe necessary for the QS state.
Date: March 23, 1999
Creator: Howes, B.D.; Ma, J.; Marzocchi, M.P.; Schiodt, C.B.; Shelnutt, J.A.; Smulevich, G. et al.
Partner: UNT Libraries Government Documents Department

Response of Cds/CdTe Devices to Te Exposure of Back Contact: Preprint

Description: Theoretical predictions of thin-film CdS/CdTe photovoltaic (PV) devices have suggested performance may be improved by reducing recombination due to Te-vacancy (VTe) or Te-interstitial (Tei) defects. Although formation of these intrinsic defects is likely influenced by CdTe deposition parameters, it also may be coupled to formation of beneficial cadmium vacancy (VCd) defects. If this is true, reducing potential effects of VTe or Tei may be difficult without also reducing the density of VCd. In contrast, post-deposition processes can sometimes afford a greater degree of defect control. Here we explore a post-deposition process that appears to influence the Te-related defects in polycrystalline CdTe. Specifically, we have exposed the CdTe surface to Te prior to ZnTe:Cu/Ti contact-interface formation with the goal of reducing VTe but without significantly reducing VCd. Initial results show that when this modified contact is used on a CdCl2-treated CdS/CdTe device, significantly poorer device performance results. This suggests two things: First, the amount of free-Te available during contact formation (either from chemical etching or CuTe or ZnTe deposition) may be a more important parameter to device performance than previously appreciated. Second, if processes have been used to reduce the effect of VTe (e.g., oxygen and chlorine additions to the CdTe), adding even a small amount of Te may produce detrimental defects.
Date: June 1, 2012
Creator: Gessert, T. A.; Burst, J. M.; Ma, J.; Wei, S. H.; Kuciauskas, D.; Barnes, T. M. et al.
Partner: UNT Libraries Government Documents Department