Room-temperature luminescence of benzo[f]quinoline, p-aminobenzoic acid, phenanthrene, and 4-phenylphenol on a variety of solid surfaces

Analytical figures of merit for the room-temperature luminescence of four model compounds with quite different chemical structures were compared. The compounds were adsorbed on four different surfaces that have been employed recently in solid-surface luminescence analysis. The solid materials investigated were silica gel with a polyacrylate binder, filter paper, 1% polyacrylic acid-NaBr, and 80% α-cyclodextrin-NaCl. The experimental conditions were optimized to give enhanced luminescence signals. In some cases, filter paper and 80% α-cyclodextrin-NaCl gave comparable analytical results. However, filter paper gave the best overall results.     

How often is a polygon bounded by three sides?

LetL _n be the set of lines (no two parallel) determining ann-sided bounded faceF in the Euclidean plane. We show that the number,f(L _n), of triples fromL _n that determine a triangle containingF satisfies and these bounds are best. This result is generalized tod-dimensional Euclidean space (without the claim that the upper bound is attainable).     

Synthesis,crystal structure,and reactivity of alkali and silver salts of sulfonated imidazoles

Both 2-methylimidazole and 2-ethyl-4-methylimidazole were monosulfonated with oleum in the five position. In crystals of the monohydrate of 2-methylimidazole-5-sulfonic acid, hydrogen bonds link the molecules into a 3-dimensional network, while in crystals of 2-ethyl-4-methylimidazole-5-sulfonic acid, corrugated 2-dimensional layers are present. The Li and Ag salts and the bis(trimethylsilyl) derivatives of 2-ethyl-4-methylimidazole-5-sulfonic acid were prepared, and there is evidence for doubly deprotonated imidazolesulfonate in aqueous solution. The monohydrate of the Li salt and the Ag salt also form a 3-dimensional, H-bonded network. Only in the Ag salt does the asymmetric unit consist of more than one basic formula unit. One Ag atom is 2-coordinate and links two nitrogen atoms, while the other Ag atom has distorted tetrahedral coordination and links the sulfonate groups into an infinite chain. Reactions of the silver salt with 1,4-dibromobutane in non-protic solvents such as 1-methyl-2-pyrrolidone were used to link two of the imidazolesulfonic acid units with a 4-carbon chain at the nitrogens.     

A collaboratory for radiation therapy treatment planning optimization research

Intensity modulated radiation therapy treatment planning (IMRTP) is a challenging application of optimization technology. We present software tools to facilitate IMRTP research by computational scientists who may not have convenient access to radiotherapy treatment planning systems. The tools, developed within Matlab and CERR (computational environment for radiotherapy research), allow convenient access, visualization, programmable manipulation, and sharing of patient treatment planning data, as well as convenient generation of dosimetric data needed as input for treatment plan optimization research. CERR/Matlab also provides a common framework for storing, reviewing, sharing, and comparing optimized dose distributions from multiple researchers.     

Summing over a network without revealing summands

Consider a network in which each node possesses a secret member of a finite abelian group. In this paper we present a protocol by which the nodes can compute the sums of their secret elements without revealing them to each other. The security against discovery of the secret values as a result of conspiracies among nodes or compromise of channels between nodes is shown to depend on the connectivity of the graph defined by the network. Moreover, we are able to quantify exactly the amount of information revealed as a result of a conspiracy of a given set of nodes or compromise of a given set of channels.     

Preparation of Phase Pure Cubic Gallium Nitride, c-GaN, by Ammonothermal Conversion of Gallium Imide, {Ga(NH)3/2} n

Gallium imide, {Ga(NH)_3/2} _n , was sealed in quartz tubes with anhydrous NH₃ and NH₄X (X=Cl, Br, I) and heated vertically in an autoclave with the hot-zone (bottom) temperature ranging from 300–530°C. With NH₄I mineralizer, the imide was converted to primarily the zinc-blende phase of GaN (c-GaN), usually in the form of micron sized or smaller tetrahedra. With NH₄Cl mineralizer, hexagonal GaN nanoparticles formed instead, and NH₄Br facilitated the conversion of imide to irregular h-GaN nanoparticles at lower temperatures, and larger particles above 500°C. At the higher temperatures, chemical transport took place and GaN crystals grew on the walls at the middle to the top of the tube. Most of the deposited GaN was cubic, usually in a heavily etched triangular prismatic morphology. Several experiments were performed in a Pt lined pressure vessel in order to demonstrate that the synthesis method can be scaled up.     

The high-performance liquid chromatography and detection of phospholipids and triglycerides: Part 2. Comparison of an ultraviolet absorption and post-column reactor detector

A liquid chromatographic ultraviolet absorption detector (at 195 nm) and a novel postcolumn reactor detector are compared for use in the detection of triglyceride and phospholipid molecular species. The detection limit for the u.v. detector depends on the degree of unsaturation of the lipid sample (3 × 10^-6–2 × 10^-8 M in the detector cell for 0–3 double bonds per acyl group). The post-column reactor detector is responsive to equivalents of lipid and has detection limits of 5 × 10^-7 M for triglycerides and 2 × 10^-6 M for phospholipids. The log u.v./post-column reactor detector response ratios are linearly related to the log of the degree of unsaturation of the lipid, indicating the usefulness of both detectors for quantifying triglycerides and phospholipids.     

Control of material damping in high-Q membrane microresonators

We study the mechanical quality factors of bilayer aluminum-silicon-nitride membranes. By coating ultrahigh-Q Si(3)N(4) membranes with a more lossy metal, we can precisely measure the effect of material loss on Q's of tensioned resonator modes over a large range of frequencies. We develop a theoretical model that interprets our results and predicts the damping can be reduced significantly by patterning the metal film. Using such patterning, we fabricate Al-Si(3)N(4) membranes with ultrahigh Q at room temperature. Our work elucidates the role of material loss in the Q of membrane resonators and informs the design of hybrid mechanical oscillators for optical-electrical-mechanical quantum interfaces.     

Structural determination of glycopeptidolipids of Mycobacterium smegmatis by high‐resolution multiple‐stage linear ion‐trap mass spectrometry with electrospray ionization

Glycopeptidolipids (GPLs) are abundant in the cell walls of different species of mycobacteria and consist of tripeptide‐amino‐alcohol core of D‐Phe‐D‐allo‐Thr‐D‐Ala‐L‐alaninol linked to 3‐hydroxy or 3‐methoxy C_26–34 fatty acyl chain at the N‐terminal of D‐Phe via amide linkage, and a 6‐deoxytalose (6‐dTal) and an O‐methyl rhamnose residues, respectively, attach to D‐allo‐Thr and the terminal L‐alaninol. They are important cell‐surface antigens that are implicated in the pathogenesis of opportunistic mycobacteria belonging to the Mycobacterium avium complex. In this contribution, we described multiple‐stage linear ion trap in conjunction with high‐resolution mass spectrometry towards structural characterization of complex GPLs as [M + Na]⁺ ions isolated from Mycobacterium smegmatis, a fast‐growing and non‐pathogenic mycobacterial species. Following resonance excitation in an ion trap, MSⁿ spectra of the [M + Na]⁺ ions of GPLs contained mainly b and y series ions that readily determine the peptide sequence. Fragment ions from MSⁿ also afford locating the 6‐dTal and O‐methyl rhamnose residues linked to the D‐allo‐Thr and terminal L‐alaninol of the peptide core, respectively, as well as recognizing the modifications of the glycosides, including their acetylation and methylation states and the presence of succinyl group. The GPL families consisting of 3‐hydroxy fatty acyl and of 3‐methoxy fatty acyl substituents are readily distinguishable. The MS profiles of the GPLs from cells are dependant on the conditions they were grown, and several isobaric isomers were identified for many of the molecular species. These multiple‐stage mass spectrometric approaches give detailed structures of GPL in complex mixtures of which the isomeric structures are difficult to define using other analytical methods. Copyright © 2012 John Wiley & Sons, Ltd.