Clustering Rules: A Comparison of Partitioning and Hierarchical Clustering Algorithms

Previous research has resulted in a number of different algorithms for rule discovery. Two approaches discussed here, the ‘all-rules’ algorithm and multi-objective metaheuristics, both result in the production of a large number of partial classification rules, or ‘nuggets’, for describing different subsets of the records in the class of interest. This paper describes the application of a number of different clustering algorithms to these rules, in order to identify similar rules and to better understand the data.     

Biogenic aldehyde determination by reactive paper spray ionization mass spectrometry

Ionization of aliphatic and aromatic aldehydes is improved by performing simultaneous chemical derivatization using 4-aminophenol to produce charged iminium ions during paper spray ionization. Accelerated reactions occur in the microdroplets generated during the paper spray ionization event for the tested aldehydes (formaldehyde, n-pentanaldehyde, n-nonanaldehyde, n-decanaldehyde, n-dodecanaldehyde, benzaldehyde, m-anisaldehyde, and p-hydroxybenzaldehyde). Tandem mass spectrometric analysis of the iminium ions using collision-induced dissociation demonstrated that straight chain aldehydes give a characteristic fragment at m/z 122 (shown to correspond to protonated 4-(methyleneamino)phenol), while the aromatic aldehyde iminium ions fragment to give a characteristic product ion at m/z 120. These features allow straightforward identification of linear and aromatic aldehydes. Quantitative analysis of n-nonaldehyde using a benchtop mass spectrometer demonstrated a linear response over 3 orders of magnitude from 2.5 ng to 5 μg of aldehyde loaded on the filter paper emitter. The limit of detection was determined to be 2.2 ng for this aldehyde. The method had a precision of 22%, relative standard deviation. The experiment was also implemented using a portable ion trap mass spectrometer.     

Energy transfer between conjugated polyelectrolytes in layer-by-layer assembled films

We present a study of Fo?rster resonance energy transfer (FRET) between two emissive conjugated polyelectrolytes (CPEs) in layer-by-layer (LbL) self-assembled films as a means of examining their organization and architecture. The two CPEs are a carboxylic acid functionalized polyfluorene (PFl-CO(2)) and thienylene linked poly(phenylene ethynylene) (PPE-Th-CO(2)). The PFl-CO(2) presents a maximum emission at 418 nm, while the PPE-Th-CO(2) has an absorption λ(max) centered at 431 nm, in sufficient proximity for effective FRET. Several LbL films have been constructed using varied concentrations of the deposition solutions and identity of the buffer layers separating the two emissive layers, using a system of either weak polyelectrolytes, poly(allylamine hydrochloride) (PAH)/poly(sodium methacrylate) (PMA), or strong polyelectrolytes, poly(diallylammonium chloride) (PDDA)/poly(styrene sulfonate) sodium (PSS). The efficiency of FRET has been monitored using fluorescence spectroscopy. Initially, the fluorescence of the PFl-CO(2) (E(g) ～ 3.0 eV), which emits at 420 nm, is quenched by the lower band gap PPE-Th-CO(2) (E(g) ～ 2.5 eV). For films using the PAH/PMA system as buffer bilayers and deposited from 1 mM solutions, the PFl-CO(2) fluorescence is progressively recovered as the number of intervening buffer bilayers is increased. Ellipsometry measurements indicate that energy transfer between the two emissive layers is efficient to a distance of ca. 7 nm.     

Use of engineered unique cysteine residues to facilitate oriented coupling of proteins directly to a gold substrate

A prerequisite for any "lab on a chip" device that utilizes an electrical signal from the sensor protein is the ability to attach the protein in a specific orientation onto a conducting substrate. Here, we demonstrate the covalent attachment to a gold surface of light-harvesting membrane proteins, from Rhodobacter sphaeroides, via cysteine (Cys) residues engineered on either the cytoplasmic or periplasmic face. This simple directed attachment is superior in its ability to retain light-harvesting complex (LHC) function, when compared to a similar attachment procedure utilizing a self-assembled monolayer on gold. LH 1 has previously been observed to have superior photostability over LH 2 (Magis et al. [2010] Biochim. Biophys. Acta, 1798, 637-645); this characteristic is maintained even with the introduction of Cys residues.     

The effect of heating temperature and nitric acid treatments on the performance of Cu- and Zn-based broad spectrum respirator carbons

Impregnated activated carbons (IACs) that are used in broad spectrum gas mask applications have historically contained copper and/or zinc impregnants. The addition of an oxidizing agent, such as nitric acid (HNO(3)) can be useful in distributing the metallic impregnants uniformly on the activated carbon substrate. In this work, we study IACs prepared from copper nitrate (Cu(NO(3))(2)) and zinc nitrate (Zn(NO(3))(2)) precursors as a function of HNO(3) content present in the impregnating solution and as a function of heating temperature. The gas adsorption capacity of the IACs was determined by dynamic flow testing using sulfur dioxide (SO(2)), ammonia (NH(3)), hydrogen cyanide (HCN) and cyclohexane (C(6)H(12)) challenge gases under dry and humid conditions. The thermal decomposition and distribution of the impregnant on the activated carbon substrate is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis techniques. Relationships between gas adsorption capacity, impregnant distribution and the species of surface impregnants are discussed.     

Progress in stacked piezocomposite ultrasonic transducers for low frequency applications

A stacked ultrasonic transducer comprises multiple individual layers connected mechanically in series and electrically in parallel to reduce the fundamental thickness mode resonance to a frequency corresponding to the transit time of the complete stack and the electrical impedance to a value which corresponds to that of the layers of the stack in parallel. In turn, this allows lower frequency resonant operation than would be possible with a single layer, and facilitates electrical impedance matching to typical transmission circuitry. On transmission, an ideal stack of uniform layers will have an output amplitude larger than that of the equivalent single layer by a factor equal to the . However, using conventional signal amplification circuitry on reception, the output voltage amplitude will be smaller than that of the equivalent single layer by a similar factor. In the past, stacks have commonly been assembled from layers of conventional piezoceramic material but more recently there have been reports of stacks of 1–3 piezocomposites and it is this type that is considered here. The work described in this paper is motivated by the need to operate at frequencies lower than are possible using conventional piezocomposite fabrication technology. Progress in comparison of experimental and simulated results is outlined and the highlights of a theoretical design study are presented. These show that although the general behaviour of a stacked structure is easily predicted, a rigorous theoretical analysis is essential to understand the detail of even a limited range of possible designs.     

Simultaneous quantification of zidovudine and its glucuronide in serum by high-performance liquid chromatography

A sensitive high-performance liquid chromatography (HPLC) assay has been developed to simultaneously determine levels of the anti human immunodeficiency virus agent, zidovudine (AZT), and its major metabolite (the 5'-O-glucuronide) in serum. Samples were first mixed with an internal standard (a stereoisomer of AZT), then prepared for analysis using solid-phase extraction columns and chromatographed using a reversed-phase analytical column. Isocratic elution with a mobile phase of 15% acetonitrile, buffered to pH 2.70 with ammonium phosphate, gave good resolution of the three analytes and endogenous serum components. The HPLC analysis time required per sample was 34 min and analyte recoveries were reproducibly high (greater than 93%). Replicate analyses of prepared standards gave satisfactory precision and accuracy, with coefficients of variation less than 15% and deviations from expected concentrations less than 10%.     

Thiocyanate-assisted demetallation of α,β,γ,δ-tetra(p-sulfophenyl)porphinatoindium(III) in aqueous media

The rate law for the demetallation of the title indium(III)-porphin complex in aqueous acidic thiocyanate media at 3.00M ionic strength was found to be of the form where [H₄P^2?] is the concentration of the diacid product formed, [InP]_t is the total concentration of all forms of indium(III)-porphin complex present, and a and b are constants. The constant a is a pseudo-third-order rate constant with the value (0.057 ± 0.005)M^?2 s^?1 and b has the value 0.704M^?2 at 50.5°C. If the mechanism for demetallation involves ringpuckering with the attachment of two H⁺ ions, then 1/b can be identified with the product K₁K₂ for the stepwise dissociation of two protons from two ring pyrrolic nitrogen atoms of H₂InP^?. In the sulfonated tetraphenylporphin used for these studies the ring pyrrolic nitrogen atoms seem to be the most probable sites for protonation. If this identification is correct, the value of 1.42 ± 0.13 found for the product K₁K₂ shows the enormous effect that the presence of the In³⁺ center has on the ionization constants of these two protons. That the kinetic studies show saturation effects with respect to proton addition to InP^3? may result from the fact that In³⁺ sits about 0.6 Å above the porphin ring.     

1,3,5-Trisubstituted hexahydrotriazines as mannich reagents. III. Preparation and cleavage of 3,4-dihydro-6-hydroxy-3-substituted-2H-1,3-benzoxazine hydrochlorides

3,4-Dihydro-6-hydroxy-3-substituted-2H-1,3-benzoxazine hydrochlorides have been prepared by the reaction of hydroquinones with novel aminomethylating reagents prepared from 1,3,5-trisubstituted hexahydrotriazines. With these monooxazine hydrochlorides is formed an equal molar amount of an amine hydrochloride. Purification leads to low yields. This difficulty has been circumvented by the use of bis(alkoxymethyl)amines in the presence of anhydrous hydrogen chlorides. The monooxazines have been hydrolyzed to yield ortho-secondary aminomethylhydro-quinone derivatives.     

A study of hand vibration on chipping and grinding operators,part II: Four-degree-of-freedom lumped parameter model of the vibration response of the human hand

The results of the development of a four-degree-of-freedom, lumped parameter model of the vibration response characteristics of the human hand are presented. For this study dynamic compliance measurements were made on 75 foundry workers. Curve fitting techniques were then employed to identify the values of the model parameters that yielded empirically generated dynamic compliance curves that correlated well with the measured dynamic compliance values. The agreement was good between 20 Hz and 1000 Hz in the X- and Y-directions. The agreement was good between 20 Hz and 1000 Hz in the Z-direction.