Schwarzschild black hole in noncommutative spaces

We study the effects of noncommutative spaces on the horizon, the area spectrum and Hawking temperature of a Schwarzschild black hole. The results show deviations from the usual horizon, area spectrum and the Hawking temperature. The deviations depend on the parameter of space/space noncommutativity.     

Determination of trace elements in tea leaves by neutron activation analysis

Instrumental neutron activation analysis has been employed to determine 14 trace elements in two brands of Iranian and foreign tea. The elements are: Br, La, Ba, K, Mn, Cl, Cr, Cs, Rb, Fe, Co, Zn, Sc and Au. The transference ratio of the elements into solution, when tea is leached by percolation, is also reported. It was found that some elements are totally transferred into solution and some are partially retained by the leaves.     

Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite

Adsorption isotherms of H₂S, CO₂, and CH₄ on the Si-CHA zeolite were measured over pressure range of 0–190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO₂ adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35–45 (2008); Surf Sci Catal 170:1021–1027 (2007)) for the pure silica DD3R zeolite while the amounts of CH₄ adsorption are reasonably the same. Si-CHA zeolite showed high ideal selectivities for acid gases over methane at 100 kPa (6.15 for H₂S and 4.06 for CO₂ at 298 K). Furthermore, H₂S adsorption mechanism was found to be physical, and hence, Si-CHA can be utilized in pressure swing adsorption processes. Due to higher amount of carbon dioxide adsorbed and lower heats of adsorption as well as three dimensional channels of Si-CHA pore structure, this zeolite can remove acid gases from methane in a kinetic based process such as zeolite membrane.     

Dispersive liquid-liquid microextraction of Fe(II) and Cu(II) with diethyldithiocarbamate and their simultaneous spectrophotometric determination using mean centering of ratio spectra

A new dispersive liquid-liquid microextraction (DLLME) method for preconcentration of trace quantities of Fe(II) and Cu(II) followed by their spectrophotometric determination has been developed. For the extraction, an appropriate mixture of ethanol (the disperser solvent) and carbon tetrachloride (the extraction solvent) was injected rapidly into the water sample containing Fe(II) and Cu(II) after formation of complexes with diethyldithiocarbamate. Mean centering (MC) of ratio spectra has been used for simultaneous determination of Fe(II) and Cu(II). Linear range of the method is 1.0–100 ng/mL for Fe(II) and 0.3–100 ng/mL for Cu(II), the detection limit is 0.53 ng/mL and 0.14 ng/mL Cu(II), resp. The interference effect of some anions and cations is reported. The method was applied to the determination of Fe(II) and Cu(II) in well water samples.     

A colorimetric sensor array for detection and discrimination of biothiols based on aggregation of gold nanoparticles

Developments of sensitive, rapid, and cheap systems for identification of a wide range of biomolecules have been recognized as a critical need in the biology field. Here, we introduce a simple colorimetric sensor array for detection of biological thiols, based on aggregation of three types of surface engineered gold nanoparticles (AuNPs). The low-molecular-weight biological thiols show high affinity to the surface of AuNPs; this causes replacement of AuNPs’ shells with thiol containing target molecules leading to the aggregation of the AuNPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of the predetermined aggregation, color and UV–vis spectra of AuNPs are changed. We employed the digital mapping approach to analyze the spectral variations with statistical and chemometric methods, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The proposed array could successfully differentiate biological molecules (e.g., cysteine, glutathione and glutathione disulfide) from other potential interferences such as amino acids in the concentration range of 10–800 μmol L⁻¹.     

Interference peaks in mass analysed ion kinetic energy spectra

When mass analysed ion kinetic energy spectroscopy is performed on ions of low abundance and low mass compared with the rest of the ions present in the ion chamber, severe interference may be observed. The major form taken by the interference is of narrow peaks at non-integral mass numbers. Many such peaks can be observed in mass analysed ion kinetic energy spectra and they are mainly attributed to decompositions of metastable ions occurring in the first field free region of the reversed geometry double focusing mass spectrometer.     

Dynamic behaviour of chlorofluoroethanes at fluorinated chromia aerogels and fluorinated zinc(II) or magnesium(II) doped chromia aerogels

The preparation and characterisation of two series of fluorinated chromia aerogel materials, lightly doped with zinc(II) or magnesium(II), are described. They behave as heterogeneous catalysts for transformations of 1,1,2-trichlorotrifluoroethane under HF-free conditions and at moderate temperatures. Product distributions depend critically on the contact time. When the latter is very long (static conditions) the surface becomes chlorinated, notwithstanding its fluorinated nature. Rather surprisingly, in view of previous work, the catalytic behaviour of the materials is almost identical to that of the undoped fluorinated chromia aerogel. The nature of reactions occurring under HF-free conditions and low levels of doping achievable are discussed as possible factors in determining catalytic behaviour.     

Identification of catecholamine neurotransmitters using fluorescence sensor array

A nano-based sensor array has been developed for identification and discrimination of catecholamine neurotransmitters based on optical properties of their oxidation products under alkaline conditions. To produce distinct fluorescence response patterns for individual catecholamine, quenching of thioglycolic acid functionalized cadmium telluride (CdTe) quantum dots, by oxidation products, were employed along with the variation of fluorescence spectra of oxidation products. The spectral changes were analyzed with hierarchical cluster analysis (HCA) and principal component analysis (PCA) to identify catecholamine patterns. The proposed sensor could efficiently discriminate the individual catecholamine (i.e., dopamine, norepinephrine, and l-DOPA) and their mixtures in the concentration range of 0.25–30 μmol L⁻¹. Finally, we found that the sensor had capability to identify the various catecholamines in urine sample.     

1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers as an efficient and reusable nanocatalyst for the synthesis of tetraketones in aqueous medium

Research on Chemical Intermediates - 1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers (CNF@DBU[Cl]) were simply prepared and characterized by analytical techniques. Scanning...     

Comparison of dry reforming of methane in low temperature hybrid plasma-catalytic corona with thermal catalytic reactor over Ni/γ-Al2O3

In the current study,the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO2 reforming of methane is investigated.The study includes both purely catalytic operation in the temperature range of 923-1023K,and hybrid catalytic-plasma operation of DC corona discharge reactor at room temperature and ambient pressure.The effect of feed flow rate,discharge power and Ni/γ-Al2O3 catalysts are studied.When CH4/CO2 ratio in the feed is 1/2,the syngas of low H2/CO ratio at about 0.56 is obtained,which is a potential feedstock for synthesis of liquid hydrocarbons.Although Ni catalyst is only active above 573K,presence of Ni catalysts in the cold corona plasma reactor(T≤523K) shows promising increase in the conversions of methane and carbon dioxide.When Ni catalysts are used in the plasma reaction,H2/CO ratios in the products are slightly modified,selectivity to CO increases whereas fewer by-products such as hydrocarbons and oxygenates are formed.