A Facile Synthesis of 3-Substituted Methyl 4,6-Dihydrothieno[3,4-b]thiophene-2-carboxylate 5,5-Dioxides as Precursors of o-Dimethylene Thiophene

A facile synthesis of 3-substituted methyl 4,6-dihydrothieno[3,4-b]thiophene-carboxylate 5,5-dioxides 1 from 3-(phenylthio)-4-acyl-3-sulfolenes 2 and their use as stable precursors of o-dimethylene thiophene 3 in [4 + 2] cycloaddition are described.     

Theoretical and experimental studies of the diketene system: Product branching decomposition rate constants and energetics of isomers

The kinetics and mechanism for the thermal decomposition of diketene have been studied in the temperature range 510–603 K using highly diluted mixtures with Ar as a diluent. The concentrations of diketene, ketene, and CO₂ were measured by FTIR spectrometry using calibrated standard mixtures. Two reaction channels were identified. The rate constants for the formation of ketene (k₁) and CO₂ (k₂) have been determined and compared with the values predicted by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory for the branching reaction. The first-order rate constants, k₁ (s⁻¹) = 10^{15.74 ± 0.72} exp(−49.29 (kcal mol⁻¹) (±1.84)/RT) and k₂ (s⁻¹) = 10^{14.65 ± 0.87} exp(−49.01 (kcal mol⁻¹) (±2.22)/RT); the bulk of experimental data agree well with predicted results. The heats of formation of ketene, diketene, cyclobuta-1,3-dione, and cyclobuta-1,2-dione at 298 K computed from the G2M scheme are −11.1, −45.3, −43.6, and −40.3 kcal mol⁻¹, respectively. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 580–590, 2007     

Simultaneous Determination of Aluminum,Cadmium and Lead in Whole Blood by Simultaneous Atomic Absorption Spectrometry with Oxygen Charring

A method for the simultaneous determination of aluminum (Al), cadmium (Cd) and lead (Pb) in whole blood has been developed by using simultaneous atomic absorption spectrometry (SIMAAS) with oxygen charring. The optimized conditions for the simultaneous determination of Al, Cd and Pb were obtained in the presence of palladium (Pd) as the chemical modifier, using 600 °C and 2400 °C as the pyrolysis and the atomization temperature, respectively. The whole blood samples were diluted 1+5 (v/v) directly with 0.1% (v/v) Triton X‐100. Oxygen was employed to eliminate the interference of carbonaceous residues in the charring step before pyrolysis. The calibration curves were carried out with aqueous standard solutions and the linear ranges were 0–40 ng mL⁻¹, 0–4 ng mL⁻¹ and 0–40 ng mL⁻¹ for Al, Cd and Pb, respectively. The detection limits were 0.96 ng mL⁻¹ (19.2 pg) for Al, 0.03 ng mL⁻¹ (0.6 pg) for Cd and 0.60 ng mL⁻¹ (12.0 pg) for Pb. The spiked recoveries of Al, Cd and Pb in whole blood were 98.0%, 100.0% and 101.7%, respectively. The accuracy of the proposed method was evaluated with the analysis of a whole blood certified reference material (Seronorm, level 2). The found concentrations were in agreement with the recommended values. The proposed method has been successfully applied to the simultaneous determination of Al, Cd and Pb in whole blood of healthy volunteers before and after eating barbecued foods.     

Buffer effects of Ag layers on magneto-optical Co/Ge(1 0 0) ultrathin films

Magnetic properties of the Co/Ag/Ge(1 0 0) films grown at room temperature and 200 K were studied by the surface magneto-optical Kerr effect (SMOKE). More than 1.5 monolayer Ag buffer layers not only effectively block the interdiffusion between the capped Co layers and the Ge(1 0 0) substrate but also stabilize the magnetic phase. The temperature and thickness dependence on coercivity measurements show that interactions upon the interfaces are strongly correlated to the microstructures.     

A tutorial and mini-review of the ICP-MS technique for determinations of transition metal ion and main group element concentration in the neurodegenerative and brain sciences

Abstract  

New techniques in the biosciences are always welcomed and important. Reviews help in updating and disseminating information in scientific fields, especially when there are many advances such as in the vital area in neuroscience. Herein is a recent review of inductively coupled plasma mass spectrometry (ICP-MS) in the context of trace elements, relating to neurodegenerative diseases. The accurate determination of such elemental distributions in Alzheimer’s disease, Parkinson’s disease, etc. allows for a better understanding of such diseases and relates to the sensitivity and scope of the ICP-MS technique. The elements detected are often “trace” and can be analyzed for both body tissues and fluids. We discuss the practical use of ICP-MS. This includes the explanations of the instrumental setup, elements and their detection limits, a brief comparison of ICP-MS with other inorganic analysis instruments, sample preparation, and the analysis method. Next, we discuss neurodegenerative disease and metal ion analysis with ICP-MS. This includes introductions to neurodegenerative diseases, tissue analysis, fluid analysis, and bioimaging of metals in brain tissue samples, and protein analysis application with metals and ICP-MS, broken down into the subtopics of (1) isotope dilution analysis, (2) related immunoassay techniques, and (3) hyphenated instrumental applications. This article is meant to be a primer for a synthetic chemist interested in utilizing this technique and is current through the middle of 2010.     

An X-Ray Analysis on Restricted Rotational Isomers of 2-Thioxo-4-oxazolidinone

The thermodynamically more stable diastereomeric rotational isomer I, of 3-(o-tolyl)-5-methyl-2-thioxo-4-oxazolidinone, which is first crystallized out in solution, shows that the ortho methyl substituent is cisoid to the methyl group of the hetero ring, and the thermodynamically less stable isomer II, crystallized later, has both methyl groups in transoid conformation, as is found in X-ray studies. The carbonyl and thiocarbonyl bonds are found to be longer in isomer II than in isomer I, which is attributed to the favored conjugation interaction of carbonyl, thiocarbonyl groups with the lone pair electrons of nitrogen, that may cause the lessened stability of isomer II.     

Multivariable state-feedback self-tuning controllers ∗

This paper describes a state-space approach for self-tuning control of a class of multivariable stochastic systems having the same number of inputs as outputs. A multivariable state-feedback self-tuning controller, based on pole-assignment concepts, is derived. The developed multivariable self-tuner can be applied to stable/unstable and minimum/non-minimum phase linear time-invariant multivariable systems. A multivariable reduced-order self-tuner and a state-feedback minimum-variance self-tuner are also derived. The simplicity and flexibility of the proposed state-space approach facilitate the practical applications of self-tuning control concepts to real systems