Synthesis and adsorption properties of colloid-imprinted mesoporous carbons using poly(vinylidene chloride-co-vinyl chloride) as a carbon precursor

A facile synthesis of micro- and mesoporous carbons has been proposed using colloidal silica nanoparticles with diameter of ∼24 nm and poly(vinylidene chloride-co-vinyl chloride) (Saran) as a carbon precursor. The resulting carbons possessed large specific surface area, ∼800 m²/g, and approximately the same volume of micro- and mesopores, each about 50% of the total pore volume. While the size of micropores was around 1 nm, the large and uniform spherical mesopores (about 24 nm) resemble the diameters of silica colloids used. Nitrogen adsorption measurements proved that these mesopores were interconnected and accessible. The well-developed microporosity was created mainly by decomposition of Saran copolymer during carbonization.     

Relationship between the liquid crystallinity and field‐effect‐transistor behavior of fluorene–thiophene‐based conjugated copolymers

A series of fluorene–thiophene‐based semiconducting materials, poly(9,9′‐dioctylfluorene‐alt‐α,α′‐bisthieno[3,2‐b]thiophene) (F8TT2), poly(9,9′‐di(3,6‐dioxaheptyl)fluorene‐alt‐thieno[3,2‐b]thiophene) (BDOHF8TT), poly(9,9′‐di(3,6‐dioxaheptyl)fluorene‐alt‐bithiophene) (BDOHF8T2), and poly(9,9′‐dioctylfluorene‐co‐bithiophene‐co‐[4‐(2‐ethylhexyloxyl)phenyl]diphenylamine) (F8T2TPA), was synthesized through a palladium‐catalyzed Suzuki coupling reaction. F8TT2, BDOHF8TT, BDOHF8T2, and F8T2TPA films exhibited photoluminescence maxima at 523, 550, 522, and 559 nm, respectively. Solution‐processed field‐effect transistors (FETs) fabricated with all the copolymers except F8T2TPA showed p‐type organic FET characteristics. Studies of the differential scanning calorimetry scans and FETs of the polymers revealed that more crystalline polymers gave better FET device performance. The greater planarity and rigidity of thieno[3,2‐b]thiophene in comparison with bithiophene resulted in higher crystallinity of the polymer backbone, which led to improved FET performance. On the other hand, the random incorporation of the triphenylamine moiety into F8T2TPA caused the polymer chains to lose crystallinity, resulting in an absence of FET characteristics. With this study, we could assess the liquid‐crystallinity dependence of the field‐effect carrier mobility on organic FETs based on liquid‐crystalline copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4709–4721, 2006     

Two-Dimensional Isotachophoresis for the Analysis of Homovanillic Acid and Vanillylmandelic Acid in Urine for Cancer Therapy Monitoring

Homovanillic acid (HVA) and vanillylmandelic acid (VMA) are routinely analyzed by HPLC with electrochemical detection after solid phase extraction for the diagnosis of neuroblastoma and phaechromocytoma. The aim of our study was to investigate whether these compounds can be determined without sample preparation using capillary isotachophoresis (ITP). For this purpose we used a commercially available instrument with two coupled capillary columns. HVA and VMA could be easily separated by ITP–ITP analysis at pH 3.4; the LODs were in the lower μmol · L⁻¹ range using conductivity detection. ITP calibration curves in spiked urine samples showed good linear correlation. However, although good correlation with HPLC analysis was also found, the ITP–ITP values were elevated compared to the HPLC values due to underlying matrix compounds in the respective zones.     

Simultaneous low-level determination of iodine and manganese in biological materials by radiochemical neutron activation analysis

A new RNAA procedure was developed for simultaneous determination of low levels of I and Mn in biological materials. The procedure is based on sample decomposition by alkaline-oxidative fusion in a mixture of Na₂O₂ + NaOH at 900°C followed by extraction of elementary iodine by chloroform. Subsequently, Mn is separated either by precipitation of hydrated MnO₂ or by extraction of the Mn-diethyldithiocarbamate complex in chloroform. The accuracy of the RNAA procedure developed was proven by analysis of several low-level biological reference materials. Detection limits of I and Mn achievable in both institutes and the degree of interference for the Mn determination due to ⁵⁶Fe(n,p)⁵⁶Mn reaction with fast neutrons are discussed.     

Facile synthesis of 9-azajulolidine and its application to post-Ullmann reactions

This Letter describes the efficient synthesis of 9-azajulolidine from readily available reagents and its utilization as an effective electron-rich ligand for post-Ullmann-type reactions, that is, for C(aryl)-heteroatom (N, O, S) bond formation reactions, with dramatically enhanced reaction rates.     

5-Arylidene Derivatives of Meldrum’s Acid as Synthons in Pyrano[4,3-b]pyran Synthesis

The reactions of 5-arylidene derivatives of Meldrum’s acid with ethyl vinyl ether or N-vinyl-2-oxazolidinone yielded trans-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, cis-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, or diastereoisomeric mixtures of pyrano[4,3-b]pyrans and reactions with 3,4-dihydro-2H-pyran afforded Michael adducts. The reactions of 5-arylidene derivatives of Meldrum’s acid with cyanoacetic acid derivatives do not provide appropriate pyrans.     

Measurement and calculation of nonlinear absorption associated with femtosecond filaments in water

We investigate the filamentation dynamics of 200 fs, 527 nm laser pulses in water. By comparing the experimental results with the numerical simulations that use an extended propagation model, the influence of several physical effects, particularly nonlinear losses and free electron plasma generation, is studied. It is shown that a set of relevant numerical values, related to multiphoton absorption, can be extracted with reasonable accuracy. PACS 42.65.Jx; 42.25.Bs     

Determination of iodine in Asian diets by epithermal and radiochemical neutron activation analysis

Samples of diets from China, Japan, Korea, India, Pakistan and Philippines were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively) within the framework of the IAEA project “Reference Asian Man”. The RNAA procedure was based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The analytical methods employed are discussed in terms of detection limits and uncertainties of the results obtained. For quality control purposes a number of NIST biological reference materials, namely diets and foods were analyzed. Results for the diet samples indicate that achieving the WHO recommended daily allowance for iodine may be a problem in most of the above given countries. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Note on the Generalized Energy Inequality in the Navier-Stokes Equations

We prove that there exists a suitable weak solution of the Navier-Stokes equation, which satisfies the generalized energy inequality for every nonnegative test function. This improves the famous result on existence of a suitable weak solution which satisfies this inequality for smooth nonnegative test functions with compact support in the space-time.