Location of direct transitions on the Λ line of the band structure of the noble metals using angle resolved photoelectron spectroscopy (ARUPS)

The triangulation method of angle-resolved photoemission for the absolute localization of direct transitions in k-space has been used on (110) and (111) faces in the ΓKLUX or (1$\text{1}$0) mirror plane in order to determine some points of the electronic bulk band structure of Cu, Ag and Au along the Λ line. It is found that the experimental points for the occupied bands and the unoccupied bands are in good agreement with recent ground state band structure calculations based on the local density functional theory.     

A new technique (COMSPARI) to facilitate the identification of minor compounds in complex mixtures by GC/MS and LC/MS: tools for the visualization of matched datasets

In the rapidly growing field of metabolomics, it is common to analyze complex biological samples by chromatography coupled to mass spectrometry. While several techniques are available for the detection of significant peaks in individual samples, it is still difficult to determine small differences between similar samples. Using conventional software, visual inspections of individual chromatograms or individual mass spectra are often of little use because the differences in the composition of small molecules are too small to be recognizable. Thus, we developed a new approach to visualizing mass spectral datasets using a tool that allows one to easily detect these small differences between mass spectra and chromatograms derived from matched samples. Using these tools on extracts from wild-type and methyltransferase knockout strains of the yeast Saccharomyces cerevisiae, we were able to readily identify those mass spectra in our data sets that were different between the wild-type and the knockout extracts and to identify the molecules involved. The software was also successfully applied to a set of LC/MS data from peptide digests that were performed with identical substrates but different enzymes. We have named this visualization tool COMSPARI (COMparision of SPectrAl Retention Information) and are making the software publicly available via Internet at.     

Trifluoromethylsulfonyl-Based Salts of BEDT-TTF: Crystal and Electronic Structures and Physical Properties11

Three 2 : 1 salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) with trifluoromethylsulfonyl-based anions N(SO₂CF₃)₂⁻, CH(SO₂CF₃)₂⁻ and C(SO₂CF₃)₃⁻ were prepared by electrocrystallization. These salts were characterized by single-crystal X-ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistivity measurements and electronic band structure calculations. (ET)₂N(SO₂CF₃)₂ is a two-dimensional (2D) metal, but its ESR spin susceptibility above 150 K shows a weakly semiconducting behavior, presumably because during ESR measurements the sample cooling rate is slow hence allowing the disordered anions to readjust their positions. (ET)₂CH (SO₂CF₃)₂ is a 2D metal and undergoes a metal-to-insulator (MI) transition at 110 K due probably to a geometry change of the donor molecule layers. (ET)₂C(SO₂CF₃)₃ is a one-dimensional (1D) metal and undergoes an MI between 180 and 240 K, which is expected to be of charge density wave type.     

Comparative statics of changes in risk on monotonically and partially responsive kinked payoffs

This paper derives two sets of necessary and sufficient conditions on the comparative statics of changes in risk under kinked payoff functions that are monotonically responsive and partially responsive to the realization of risk, respectively. The former case includes the newsboy problem with backorder; the latter case includes the newsboy problem without backorder and under some restrictions, also includes the optimal deductible insurance problem. Some relatively non-restrictive conditions derived from the necessary and sufficient conditions reveal that the three problems can be quite different, even though they are often viewed in the literature as being congruous. These conditions lead to simple predictions of the direction of change in any risk-averse agent’s optimal choice upon a change in risk, without assuming specific functional forms for the utility function.     

Segmentation of CT brain images using unsupervised clusterings

In this paper, we present non-identical unsupervised clustering techniques for the segmentation of CT brain images. Prior to segmentation, we enhance the visualization of the original image. Generally, for the presence of abnormal regions in the brain images, we partition them into 3 segments, which are the abnormal regions itself, the cerebrospinal fluid (CSF) and the brain matter. However, for the absence of abnormal regions in the brain images, the final segmented regions will consist of CSF and brain matter only. Therefore, our system is divided into two stages of clustering. The initial clustering technique is for the detection of the abnormal regions. The later clustering technique is for the segmentation of the CSF and brain matter. The system has been tested with a number of real CT head images and has achieved satisfactory results.     

Kinetic model of the oxidation of ZrSi<Subscript>2</Subscript> powders

The oxidation kinetics of Zr-disilicide (ZrSi₂) powders up to temperatures of 1550°C were studied in flowing air using non-isothermal and isothermal thermogravimetric (TG) analysis. During the oxidation process two main thermal events were detected. The first stage of the oxidation reaction leads to the formation of elemental silicon as an intermediate reaction product. Upon further temperature increase the newly formed silicon is oxidized. Completely oxidized ZrSi₂ samples consist of ZrSiO₄, amorphous and crystalline SiO₂ as well as some residual ZrO₂. The experimental TG data were analysed with a model-fitting kinetic method. The gas-solid reaction is complex and can best be fitted with a multi-step reaction scheme consisting of branching reactions based on 3D diffusion mechanisms and a fractal order reaction.     

Synthesis,structural characterization,and photophysical studies of hexanuclear gold(I) chalcogenido complexes

A hexanuclear gold(I) selenido cluster and its sulfido counterpart, [Au₆{μ‐Ph₂PN(CH₂‐o‐Py)PPh₂}₃(μ₃‐E)₂](ClO₄)₂ (E = S, Se), with bridging bis(diphenylphosphino)amine ligands were synthesized and characterized. The X‐ray crystal structure of the selenido cluster was determined, with the gold core possessing a distorted heterocubane structure. Intramolecular aurophilic interactions with short Au(I)?Au(I) contacts of around 3.09–3.13 Å were observed. The complexes were found to emit strongly in the solid state with orange to red emission colors. Their electronic absorption and emission properties were also investigated.     

Multiwalled Carbon Nanotubes Produced by a Continuous CVD Method and Their Use in Melt Mixed Composites with Polycarbonate

Summary: In this study, two samples of multiwalled carbon nanotubes (MWNT) were synthesized by CVD of acetylene over Fe₂Co catalysts supported by CaCO₃ using different temperatures. The material produced at 660 °C (MWNT600) shows slightly better performance as evidenced by lower mean tube diameter and better conductivity as compared to the sample produced at 700 °C (MWNT700). In addition, it has a higher [O]:[C] ratio. Both materials were incorporated into polycarbonate using melt mixing using a small scale compounder. The results prove that these materials are very suitable for polymer composite applications as they show low electrical percolation concentration and good mechanical enhancement. The percolation threshold is as low as <0.875 wt% for MWNT660 and <1 wt% for MWNT700. MWNT700 showed slightly better dispersability as evidenced from light microscopy, SEM, and TEM. The effects in the stress-strain curves are similar in both composites, indicating a stress increase with MWNT incorporation.