QScience Connect - Volume 2012, Issue 1

The operational feasibility temperature range of chemical looping combustion (CLC) and chemical looping reforming (CLR) of the fuels methane, propane, iso-octane and ethanol was explored using the common sulphates Na 2SO 4, CaSO 4 and MgSO 4 as oxygen carriers. The chemical reaction equations for each oxygen carrier and fuel were formulated and fed into the Chemical Equations module of HSC Chemistry 5.1 software to obtain the Gibbs free energy change (G) of the chemical reaction within the temperature range (200–1200^∘C). The CLC and CLR process operational feasibility temperature range for the fuel-oxygen carrier combination was mapped excluding the undesirable formation of SO 2 in CLC and H 2S and S in CLR. Na 2SO 4 and CaSO 4 were found to be suitable for all CLC and CLR systems. MgSO 4 was not found to be a suitable candidate for CLC or CLR processes irrespective of the fuel considered. Methane was found to be better than the other fuels studied as the operational temperature range of CLC and CLR processes were wide for all the sulphates. This short cut methodology presented in this paper can be used to predict the operational feasibility of CLC and CLR processes of different fuels and oxygen carriers.

Background: Organophosphorus compounds have important industrial and biomedical applications as pharmaceutical and agrochemical agents, as well as transition state analogs for the production of monoclonal antibodies.

Methods: Two diastereomers of a 6-membered ring, cyclic phenyl phosphonate were synthesized in 8 steps from 1,3-butanediol.

Results: The stereochemistry of the diastereomers was elucidated on the basis of P NMR signals, together with H NMR nuclear Overhauser effects (NOE) difference experiments.

Conclusions: Such cyclic phosphonates may have utility serving as transition state analogs for the production of monoclonal antibodies.

The study of phytoplankton diversity and its seasonal variation was carried out by sampling water taken from the Santragachi Lake, of West Bengal between November 2009 and July 2010. Various physico-chemical variables were recorded and the correlation of this with phytoplankton density was established using Canonical Correspondence Analysis. This showed that the density of phytoplankton was higher when temperature and nutrients were increased. A total of 29 phytoplankton taxa belonging to Chlorophyta (10), Cyanobacteria (8), Charophyta (5), Bacillariophyta (4), and Euglenozoa (2) were recorded from nine samples taken within the study period. Chlorophyta species dominated mostly in variety and percentage composition while Euglenozoa species representatives had the least expression. Bio-indication showed a low diverse community in the monsoon period with better water quality than in pre- and post-monsoon seasons. Various diversity indices (Shannon–Wiener diversity index, Gleason species richness index, Pielou evenness index, and Naughton dominance index) were used to establish the seasonal variation of phytoplankton. The Shannon–Wiener diversity index was most useful in indicating the trophic status of the water as well as the pollution status, which in this case, depicted a moderate level of pollution of this lake.

The petroglyph site in Jabal Jassasiyah Qatar is located approximately 60 km northeast of the capital city of Doha and has over 900 different types of petroglyphs. The most commonly found petroglyphs are cupules, which are almost always arranged in geometric patterns. A number of petroglyphs of boats are also found, usually seen from above, with a few seen in profile. As there is little evidence of what age to assign to these petroglyphs, samples of the calcium oxalate containing layers covering the petroglyphs were sent for radiocarbon dating to determine the minimum age they were created. The minimum ages of nine samples taken for analysis were found to be very short, the oldest minimum age being only 235 years BP (before present). No evidence was found for the petroglyphs dating back a few millennia as was previously postulated. Due to the lack of chronological data for Qatar’s archaeological past, the study data cannot completely rule out the petroglyphs dating back to ancient times.

Background: The incidence of oral indigenous bacteria in cases of bacteremia has been reported in only a few studies. We investigated the annual incidence of oral indigenous bacteria isolated in blood cultures from patients with bacteremia and call into consideration the impact of oral health measures implemented at our facility.

Methods: In the period from 2001 to 2006, 759 laboratory-confirmed cases of bacteremia were reported and subsequently analyzed in this study. The incidences of the causative strain and oral indigenous bacteria in blood cultures were studied by year.

Results: In 759 cases of bacteremia, oral streptococci were noted in 14 (1.8%), and anaerobic bacteria were noted in 9 (1.2%). The population of microorganisms did not change significantly during the study period.

Conclusions: In a previous report, oral streptococci accounted for 3.8% of those under investigation. In this study, the incidence of oral streptococci was significantly low, 1.8% specifically. A focus on oral health care at our hospital may account for a reduced incidence of oral streptococci bacteremia.

Background: Synthetic cationic lipids hold much potential as gene packaging and delivery agents for the treatment of inherited and acquired life threatening diseases, such as cancer, AIDS, cardiovascular diseases, and certain autoimmune disorders. Methods: We report the synthesis, self-assembly as characterized by critical micelle concentrations and plasmid DNA gel retardation using two novel cyclic, phosphonate cationic lipids 2a and 2b, which were synthesized by derivatizing two diastereomeric macrocyclic phosphonates 1a and 1b with a 2-carbon hydroxylamine linker, N, N-dimethylethanolamine (3). Results: The production of cyclic phosphonate lipids 2a and 2b in 73% and 60% yields, respectively, was achieved using classical synthetic methods involving nucleophilic substitution at the phosphorus centre. The characterization of these lipids with Mass Spectrometry, ¹H, ¹³C and ³¹P Nuclear Magnetic Resonance supported the proposed stereochemistry and molecular structure of C17H36NO3P for these lipids. Critical micelle concentrations (CMC) for 2a and 2b were found to be 1.2 mM and 1.4 mM, respectively, at 25°C, providing evidence for the self-assembling ability of these novel cyclic lipids. Finally, lipid-DNA complexes (lipoplexes) formulated at various N/P (+/ − ) molar charge ratios and containing the co-lipid, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) were shown to retard DNA in an agarose gel retardation assay. Conclusions: The synthesis, aggregation and DNA binding properties of these novel cyclic phosphonate lipids suggest that they may have utility serving as gene packaging and delivery agents.

The optimal conditions of liquid–liquid extraction of two synthetic phenolic antioxidants, BHA and BHT were investigated in five Iranian edible vegetable oil samples using the central composite design. Stepwise multiple linear regression method was used for construction of different models based on the experimental data. Optimum conditions for BHA and BHT were achieved using 3 ml of ethanolic solution containing (0.25% v/v) of glacial acetic acid, three extractions and a mixing time of 10 minutes. Analytes were separated using HPLC with a C 18 column using methanol:water:glacial acetic acid (75:24:1, v/v/v) as the mobile phase. The limit of detections, linear ranges and relative standard deviation () were 0.04 μg/g⁻¹, 0.5– 200 μg/g⁻¹ and 2.6% for BHA and 0.30 μg/g⁻¹, 1.0– 200 μg/g⁻¹ and 4.20% for BHT, (), respectively. Amounts of BHA and BHT in analyzed oil samples were in the ranges of 29.8– 54.5 μg/g⁻¹ and 0.0– 6.8 μg/g⁻¹ respectively.

N,N-disubstituted bis(furanyl-2-methyl)aminoanilines are new electrochemically-active probes for cations relying on the phenylenediamine moiety as an electroactive transducer and the difuranylamino group as an ionophore site. The electrochemical investigations, by means of cyclic and Osteryoung square wave voltammetries (CV and SWV, respectively), showed that these compounds are able to bind Mg²⁺, Ca²⁺, Ni²⁺ and Zn²⁺ cations with strong affinities. The addition of catalytic amounts of trifluoromethanesulfonic acid (TfOH) was found necessary to achieve rapid cation complexation. The electroactive redox features of the probes were drastically modified when the ionophore site was bonded to the cations. The anodic potential shifts of the oxidation peaks were between 905 and 1030 mV depending on the cations. The electrochemical investigations suggested the formation of a 1:2 stoichiometric complex: [M(L) 2]²⁺, M=Mg, Ca, Ni and Zn. These probes were found to be selective of Ca²⁺ and chelates, with strong preference for Ca²⁺ even in presence of others cations (Ca²⁺> Mg²⁺, Ca²⁺> Ni²⁺ and Ni²⁺> Zn²⁺). UV-visible spectrophotometric studies also showed blue shifts of the absorption bands comprising between 5 and 29 nm ligands when the metal ions were added to the solution, which confirmed the complexes formation.

In this review, the story of Qatar’s economic emergence is told chronologically, beginning with Qatar’s independence and the discovery of the North Field gas reservoir in 1971 and ending with the steps that Qatar is now taking as it transitions towards a more diversified and innovative economy.

Background: Attempts to optimize the synthetic yield of known macrocyclic phosphonates resulted in the discovery of two new macrocyclic bisphosphonate dimers. Methods: An attempt was carried out to optimize the yield of a known macrocyclic bisphosphonate dimer, 6, over the yield of monomers 2 and 3, using the Mitsunobu protocol in the macrocyclization step. Cyclization reactions were carried out at 0.003 M, 0.004 M, 0.005 M, 0.008 M and 0.02 M, compared to 0.002 M in our initial report of the synthesis of monomers. Results: In this attempt to optimize the production of dimer 6, two new macrocyclic diastereomers of 6, namely 28-membered bisphosphonates 9 and 10, were isolated in yields of 3% and 2%, respectively, and characterized by FTIR, LC-MS, , and NMR as well as by X-ray crystallography. Conclusions: The results described herein further illustrate the utility of the Mitsunobu macrocyclization (ring-closing) reaction toward the synthesis of macrocyclic phosphonates. The X-ray crystallographic characterization of the three bisphosphonate dimers, together with correlations to specific and NMR resonances allowed for the assignments of relative stereochemistries between the various dimers.

The inheritance mechanism for plant height, days to heading, spike length, grains spike^− 1 and biological yield traits in 8 × 8 half diallel F2 wheat populations was studied at Agricultural University, Peshawar, Pakistan, during 2006-07. The experiment was laid out in randomized complete block (RCB) design having four replications. Each experimental unit was assigned a four-row plot of 5 m length with row-row space of 30 cm. Analyses of variance displayed significant genotypic differences for studied traits. Diallel analyses reflected significance of both additive and non-additive components in the inheritance of these traits, however, genetic components revealed the importance of a non-additive component. The average degree of dominance being greater than unity indicated involvement of over-dominance for phenotypic expression of all traits studied. Broad-sense heritability values were much higher than narrow-sense and thus delayed selection till advance generations are suggested.

We present a geometric, model-independent, argument that aims to explain why the Tsallis entropy describes systems exhibiting “weak chaos”, namely systems whose underlying dynamics has vanishing largest Lyapunov exponent. Our argument relies on properties of a deformation map of the reals induced by the Tsallis entropy, and its conclusion agrees with all currently known results.