Semi‐supervised linear discriminant analysis

Fisher's linear discriminant analysis is one of the most commonly used and studied classification methods in chemometrics. The method finds a projection of multivariate data into a lower dimensional space so that the groups in the data are well separated. The resulting projected values are subsequently used to classify unlabeled observations into the groups. A semi‐supervised version of Fisher's linear discriminant analysis is developed so that the unlabeled observations are also used in the model‐fitting procedure. This approach is advantageous when few labeled and many unlabeled observations are available. The semi‐supervised linear discriminant analysis method is demonstrated on a number of data sets where it is shown to yield better separation of the groups and improved classification over Fisher's linear discriminant analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Roles of the Synergistic Reductive O-Methyltransferase GilM and of O-Methyltransferase GilMT in the Gilvocarcin Biosynthetic Pathway

Two enzymes of the gilvocarcin biosynthetic pathway, GilMT and GilM, with unclear functions were investigated by in vitro studies using purified, recombinant enzymes along with synthetically prepared intermediates. The studies revealed GilMT as a typical S-adenosylmethionine (SAM) dependent O-methyltransferase, but GilM was identified as a pivotal enzyme in the pathway that exhibits dual functionality in that it catalyzes a reduction of a quinone intermediate to a hydroquinone, which goes hand-in-hand with a stabilizing O-methylation and a hemiacetal formation. GilM mediates its reductive catalysis through the aid of GilR that provides FADH(2) for the GilM reaction, through which FAD is regenerated for the next catalytic cycle. This unusual synergy eventually completes the biosynthesis of the polyketide-derived defuco-gilvocarcin chromphore.     

Nanostructures versus solid solutions: low lattice thermal conductivity and enhanced thermoelectric figure of merit in Pb9.6Sb0.2Te10-xSex bulk materials

The series of Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x) compounds with different Se content (x) were prepared, and their structure was investigated at the atomic and nanosized regime level. Thermoelectric properties were measured in the temperature range from 300 to 700 K. The Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x) series was designed after the refinement of the single-crystal structure of Pb(3.82)Sb(0.12)Te(4) (Pb(9.6)Sb(0.3)Te(10); S.G. Pmm) by substituting isoelectronically in anion positions Te by Se. The Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x)() compounds show significantly lower lattice thermal conductivity (kappa(L)) compared to the well-known PbTe(1)(-)(x)Se(x) solid solutions. For Pb(9.6)Sb(0.2)Te(3)Se(7) (x = 7), a kappa(L) value as low as 0.40 W/m.K was determined at 700 K. High-resolution transmission electron microscopy of several Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x) samples showed widely distributed Sb-rich nanocrystals in the samples which is the key feature for the strong reduction of the lattice thermal conductivity. The reduction of kappa(L) results in a significantly enhanced thermoelectric figure of merit of Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x) compared to the corresponding PbTe(1)(-)(x)Se(x) solid solution alloys. For Pb(9.6)Sb(0.2)Te(3)Se(7) (x = 7), a maximum figure of merit of ZT approximately 1.2 was obtained at approximately 650 K. This value is about 50% higher than that of the state-of-the-art n-type PbTe. The work provides experimental validation of the theoretical concept that embedded nanocrystals can promote strong scattering of acoustic phonons.     

Synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones utilizing pyrrole Weinreb amides

A regiocontrolled synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones has been achieved in three steps from 1,2-diaryl-1-nitroethenes with pyrrole-2-carboxamides (pyrrole Weinreb amides) serving as the key linchpin intermediates. Two different methods for the preparation of the requisite nitroalkenes were investigated: (1) modified Henry reaction between arylnitromethanes and arylimines; and (2) Suzuki-Miyaura cross-coupling reaction of 2-aryl-1-bromo-1-nitroethenes with arylboronic acids. Some difficulty was encountered in the preparation of arylnitromethanes, thus leading to the exploration of a cross-coupling strategy that proved more useful. A Barton-Zard pyrrole cyclocondensation reaction between 1,2-diaryl-1-nitroethenes and N-methoxy-N-methyl-2-isocyanoacetamide gave the corresponding pyrrole Weinreb amides, which were then converted into the desired 3-pyrrolin-2-ones in two steps. Overall, this method allowed for the construction of 3,4-diaryl-3-pyrrolin-2-ones with complete regiocontrol of the substituents with respect to the lactam carbonyl. The utility of this synthetic methodology was demonstrated by the preparation of eight unsymmetrical and symmetrical 3,4-diaryl-3-pyrrolin-2-ones including the N-H lactam analogue of the selective COX-II inhibitor, rofecoxib.     

Binary subtrees with few labeled paths

We prove several quantitative Ramseyan results involving ternary complete trees with {0,1}-labeled edges where we attempt to find a complete binary subtree with as few labels as possible along its paths. One of these is used to answer a question of Simpson??s in computability theory; we show that there is a bounded ?? ₁ ⁰ class of positive measure which is not strongly (Medvedev) reducible to DNR₃; in fact, the class of 1-random reals is not strongly reducible to DNR₃.     

Needle and seed segmentation in intra-operative 3D ultrasound-guided prostate brachytherapy

In order to guide the needle to the correct location in 3D US-guided brachytherapy, the needle is continuously tracked as it is being inserted. A pre-scan before the needle insertion and a post-scan after the needle insertion are subtracted to obtain a difference image containing the needle. The image is projected along two orthogonal directions approximately perpendicular to the needle, and the 3D needle is reconstructed from the segmented needles in the two projected images. The seeds implanted with the needle are located in the cropped volume along the needle. Thus, the seeds are segmented using a tri-bar model and 3D line segment patterns. Finally, the positions of the seeds are determined using a peak detection technique. Experiments with agar and turkey/chicken phantoms as well as patient data demonstrated that our needle segmentation technique could segment the needle in near real-time with an accuracy of 0.6 mm in position and 1.0 degrees in orientation. The true-positive rate for seed segmentation is 100% for the agar phantom and 93% for the chicken phantom. The average distance to manual seed segmentation was 1.0mm for the agar phantom and 1.7 mm for the chicken phantom.