A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet‐like crystal morphology, large surface area, fully four‐coordinated Al species, and abundant acidic sites. Methanol‐to‐propylene (MTP) tests reveal that the Al‐ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM‐5. FCC tests show that Al‐ITH zeolite is a good candidate as a shape‐selective FCC additive for enhancing propylene and butylene selectivity.     

Oxaphospholes and Bisphospholes from Phosphinophosphonates and α,β‐Unsaturated Ketones

The reaction of a {W(CO)₅}‐stabilized phosphinophosphonate 1 , (CO)₅WPH(Ph)? P(O)(OEt)₂, with ethynyl‐ ( 2 a – f ) and diethynylketones ( 7 – 11 , 18 , and 19 ) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)₃Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5‐dihydro‐1,2‐oxaphospholes 3 and 4 . When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)₃Si or (Et)₃Si acetylene terminus is present, as in 7 , 8 , and 19 , an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene‐decorated oxaphospholes 14 , 15 , 24 , and 25 . Diacetylenic ketones 10 and 11 , with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl‐bridged bisphospholes 16 and 17 . Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene‐decorated oxaphospholes is more exothermic for the trimethylsilyl‐containing substrates. The pathway to the latter compounds contains a 1,3‐shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3‐shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high‐lying transition state TS(E′–F′)_R=Ph of 37 kcal mol^?1 is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl‐terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17 .     

Above-threshold ionization of hydrogen and hydrogen-like ions by X-ray pulses

This paper adresses the problem of above-threshold ionization (ATI) of hydrogen interacting with an intense X-ray electromagnetic field. Two approaches have been used. In the first approach, we calculate generalized differential and total cross sections based on second-order perturbation theory for the electron interaction with a monochromatic plane wave, with the A ² and A · P contributions from the nonrelativistic Hamiltonian (including retardation) treated exactly. In the second approach, we solve the time-dependent Schrödinger equation (TDSE) for a pulsed plane wave using a spectral approach with a basis of oneelectron orbitals, calculated with L ²-integrable B-spline functions for the radial coordinate and spherical harmonics Y _lm for the angular part. Retardation effects are included up to O(1/c), they induce extra terms forcing the resolution of the TDSE in a three dimensional space. Relativistic effects [of O (1/c ²)] are fully neglected. The isoelectronic series of hydrogen is explored in the range Z = 1 ? 5 in both TDSE and perturbative approaches. Photoelectron angular distributions are obtained for photon energies of 1 keV and 3 keV for hydrogen, and photon energy of 25 keV for the hydrogenic ion B⁴⁺. Perturbative and TDSE calculations are compared.     

Physico-chemical study of norfloxacin and metronidazole binary mixtures

Journal of Thermal Analysis and Calorimetry - The physico-chemical characterization of norfloxacin commercial sample (NF), norfloxacin anhydrous form A (NFanhA), norfloxacin pentahydrate...     

Optimal control for linear discrete-time systems with Markov perturbations in Hilbert spaces

Email: vio{at}utgjiu.ro Received on September 12, 2007; Accepted on December 26, 2008 In this article, we discuss a quadratic control problem forlinear discrete-time systems with Markov perturbations in Hilbertspaces, which is linked to a discrete-time Riccati equationdefined on certain infinite-dimensional ordered Banach space.We prove that under stabilizability and stochastic uniform observabilityconditions, the Riccati equation has a unique, uniformly positive,bounded on N and stabilizing solution. Based on this result,we solve the proposed optimal control problem. An example illustratesthe theory.     

Effect of strontium addition on europium-doped ceria properties

Nanopowders of composition Ce_0.9(Eu_1 ? xSr_x)_0.1O_2 ? δ (x = 0, 0.1, 0.3, 0.5, and 0.7) were prepared by the Pechini method. The microstructure and properties of powders and sintered ceramics are discussed in this paper. X-ray diffraction (XRD) and Raman spectroscopy revealed that all powders calcined at 550 °C were single phase, with the cubic fluorite-type structure. The good sintering properties of the synthesized nanopowders allowed us to obtain dense ceramics (> 96% theoretical density). Dense ceramics with density higher than 96% of the theoretical value were obtained without the need of sintering aid. The morphology of the sintered ceramics was evidenced by scanning electron microscopy (SEM). The ionic conductivities of doped and co-doped ceria ceramics were investigated as a function of temperature by using AC impedance spectroscopy in the temperature range 250–800 °C. Impedance spectra indicate a significant diminution of grain boundary resistance after partial substitution of Eu with Sr in europia-doped ceria sample, especially in the low and intermediate-temperature range. The best conductivity was evidenced for the Ce_0.9Eu_0.09Sr_0.01O_2 ? δ composition.     

Viability study of clinical bacterial strains by capillary electrophoresis and flow cytometry approaches

One of the challenges medicine faces is the constantly growing resistance of pathogens to various classes of antibiotics. In this study, we investigated the use of capillary electrophoresis (CE) to characterize and assess the physiological states of three clinical bacterial strains—methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA), and Escherichia coli extended-spectrum β-lactamases (ESβL)—exposed to different antibiotics. All chosen bacteria are the leading causes of healthcare-associated and hospital-acquired invasive infections in adults. In the first part of the research, it was determined the optimal incubation time of the tested strains with antibiotics, represented as an optimal time of 24 h. In the second part, we have compared two approaches: flow cytometry (FC) as a standard method and CE as a proposed alternative approach. The viability of clinical strains treated with different class antibiotics calculated in CE measurements was strongly correlated (>0.83 for MSSA, >0.92 for ESβL and MRSA) with the viability obtained on the basis of FC measurements. As a result, CE has a chance to become a modern diagnostic method used in clinical practice. The CE cutoff was found to be 50%; above this value, the strain shows resistance to the action of the antibiotic.     

Evaluation of gas chromatography coupled with ion mobility spectrometry for monitoring vinyl chloride and other chlorinated and aromatic compounds in air samples

The objective of this research was to evaluate, in the laboratory, the potential of gas chromatography/ion mobility spectrometry (GC/IMS) for monitoring vinyl chloride and other organic compounds in air samples in the field. It was determined that GC/IMS has the potential to directly detect vinyl chloride in air at the 2 ppbv level, and when concentrated on an adsorbent trap from a 1 L sample of air, detection could be lowered to the 0.02 ppbv level. From a comparative investigation of 18 EPA priority pollutants and 34 common vapor-phase organic compounds, many compounds were found to provide a more sensitive response in IMS than vinyl chloride, indicating that GC/IMS would be broadly applicable to the direct detection of vapor-phase organics in air. Operating parameters including drift gas, spectrometer temperature, and sample-inlet position were evaluated and discussed with respect to sensitivity and resolution. High temperature dramatically increased sensitivity to vinyl chloride. Vinyl chloride was shown to produce both negative and positive ion mobility spectra, with the negative-mode spectra resulting from electron-capture dissociation of the vinyl chloride. The limit of detection for vinyl chloride was found to be 7 pg/s. Limits of detection for 18 EPA priority pollutants were determined and compared to vinyl chloride. The responses of 34 other vapor-phase organic compounds were also compared to that of vinyl chloride. Non-selective, positive-ion detection of 30 of the 34 compounds was demonstrated along with selective, electron-capture-type detection of 29 of them. Chloride-specific and bromide-specific detection illustrated the advantages of selected-ion monitoring in IMS.     

Synthesis and Characterisation of Polyamides Containing 1,4‐Dithiin‐2,3 : 5,6‐tetrayl Diimide Structures

Polyamides containing 1,4‐dithiin‐2,3 : 5,6‐tetrayl diimide structures were synthesised by condensation reaction of bis[N,N′‐(4‐chlorocarbonylphenyl)‐1,4‐dithiin‐2,3 : 5,6‐tetrayl diimide] ( 3 ) with various aromatic diamines. Monomer 3 was synthesised by nucleophilic substitution of N‐(4‐carboxyphenyl)‐3,4‐dichloromaleimide ( 1 ) with sodium sulfide nonahydrate. Their structures were confirmed by IR and UV spectroscopy, as well as elemental analysis. The polymers were characterised by viscometric measurements, softening points and thermogravimetric data. They showed good solubility in aprotic solvents and high thermal stability with the decomposition temperature being in the range 392–415°C.