Interaction between explosive and analyte layers in explosive matrix-assisted plasma desorption mass spectrometry

An HMX/insulin two-layer system was chosen as a model for further investigation of the matrix properties of explosive materials for protein analytes in plasma desorption mass spectrometry. The dependencies of the molecular ion yield and average charge state as a function of the analyte thickness were studied. An increase in the charge state of multiply protonated molecular species was confirmed as the major matrix effect, with the average charge state z at the smallest thickness studied being higher than in matrix-assisted laser desorption/ionization and closer to the value obtained in electrospray ionization under standard acidic conditions. Observed charge state distributions are significantly narrower than the corresponding Poisson distributions, which suggests that the protonation of insulin is limited in plasma desorption by the number of basic sites in the molecule, similar to electrospray ionization. Both the curve displaying total molecular ion yield and the one showing the total charge (proton) yield as a function of the insulin thickness have maxima at a thickness different from an insulin monolayer. These observations diminish the significance of a matrix/analyte interface mechanism for the explosive matrix assistance. Instead, a mechanism related to the chemical energy release during conversion of the explosive after the ion impact is proposed. As additional mechanisms, enhanced protonation of the analyte through collisions with products of the explosive decay is considered, as well as electron scavenging by other products, which leads to a higher survival probability of positively charged protein molecular ions. Copyright 1999 John Wiley & Sons, Ltd.     

Generalized semi-closed functions and semi-generalized closed functions in bitopological spaces

In this paper we introduce and investigate the notions of a new class of generalized semi-closed functions and a class of semi-generalized closed functions in bitopological spaces. We study the further properties of ij-generalized semi closed and ij-semi-generalized closed sets. Applying of these concepts of sets, we introduce and study two new spaces, namely pairwise generalized s-regular and pairwise s-normal spaces.     

Entropic Uncertainty for Two Coupled Dipole Spins Using Quantum Memory under the Dzyaloshinskii–Moriya Interaction

In the thermodynamic equilibrium of dipolar-coupled spin systems under the influence of a Dzyaloshinskii–Moriya (D–M) interaction along the z-axis, the current study explores the quantum-memory-assisted entropic uncertainty relation (QMA-EUR), entropy mixedness and the concurrence two-spin entanglement. Quantum entanglement is reduced at increased temperature values, but inflation uncertainty and mixedness are enhanced. The considered quantum effects are stabilized to their stationary values at high temperatures. The two-spin entanglement is entirely repressed if the D–M interaction is disregarded, and the entropic uncertainty and entropy mixedness reach their maximum values for equal coupling rates. Rather than the concurrence, the entropy mixedness can be a proper indicator of the nature of the entropic uncertainty. The effect of model parameters (D–M coupling and dipole–dipole spin) on the quantum dynamic effects in thermal environment temperature is explored. The results reveal that the model parameters cause significant variations in the predicted QMA-EUR.     

On-line delta(18)O measurement of organic and inorganic substances

A method for the automated sample conversion and on-line oxygen isotope ratio (delta(18)O) determination for organic and inorganic substances is presented. The samples are pyrolytically decomposed at 1400 degrees C in the presence of nickelized graphite. With the system presented organic as well as inorganic samples such as nitrates, sulphates and phosphates of 50-100 &mgr;g O can be analyzed for their delta(18)O values with a standard deviation usually better than 0.5 per thousand. Additionally, carbon isotope ratios of organic substances and nitrogen isotope ratios of inorganic nitrogenous compounds are available in the same sample run. Data for international and some inter-laboratory reference materials are presented to show the accuracy and reliability of the method. The effect of some additives on the CO yield was checked for substances which do not pyrolyze completely. Copyright 1999 John Wiley & Sons, Ltd.     

Wave scattering effects in elastic percolation models

The study of the propagation of waves in randomly diluted models is presented. Porosity (crack-like) models are simulated by constructing typical elastic percolation networks with random microscopic heterogeneities in order to resemble rock media. Central and bond-bending forces (Born Hamiltonian) models are considered. For each experimental case, the elastic energy of the system is relaxed in equilibrium and then the model is excited by a pulse source in order to produce wave propagation. First, a review is presented of the well established velocity-porosity relationship from rock physics, which shows a linear trend from small porosities up to the critical porosity (percolation threshold) where the rocks fall apart. From the wave propagation analysis a general trend is observed for the attenuation of waves, from the small to the large porosity models, suggesting multiple scattering effects similar to those reported from effective-medium approximations of wave scattering due to random heterogeneities. Finally, the results are compared with those obtained from laboratory experiments on dry rocks with different porosities and different applied stress regimes.     

In-depth micro-spectrochemical analysis of archaeological Egyptian pottery shards

Old Egyptian pottery samples have been in-depth microchemically analyzed using laser induced breakdown spectroscopy (LIBS), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) techniques. Samples from two different ancient Islamic eras, Mamluk (1250–1517 AD), Fatimid (969–1169 AD) in addition to samples from the Roman period (30 BC–395 AD) were investigated. LIBS provided the analytical data necessary to study in micrometric steps the depth profiling of various elements in each sample. Common elements such as silicon, calcium, and aluminum relevant to the originally manufactured and processed clay, showed up in all the investigated samples. EDX and XRD techniques that have been used in the present work provided important chemical insight about the structure of the samples. The obtained analytical results demonstrated the possibility of using LIBS technique in performing in situ spectrochemical analysis of archaeological pottery. This leads to fast in-depth spatial characterization of the samples in the micron range with nearly invisible surface destructive effects. There is no doubt that this can help in restoration and conservation of such precious objects.     

Synthesis and Characterization of New Nano-Sized Selenium Compounds to Further Use as Antioxidants Drugs

Russian Journal of General Chemistry - Here we report the studies on selenium coordination compounds, in particular selenium nanoparticles (Nps), that can be used in pharmacology. The Se Nps were...     

Synthesis and modification of multi-walled carbon nano-tubes (MWCNTs) for water treatment applications

Synthesis of MWCNTs by chemical vapor deposition (CVD) of acetylene is investigated at different temperatures. Fe-Co/CaCO₃ catalyst/support prepared by wet impregnation method is used. CaCO₃ was found to be a good support as a high selective material for deposition of CNTs with high purity. The effect of temperature on catalyst/support phases and crystal size was identified by using XRD. The crystallite size was decreased with increase temperature. The effect of growing time and temperature on carbon yield was studied and the deposited MWCNTs increased with temperature. The structure and purity of synthesized CNTs at different temperatures was examined by TEM and the effect of temperature on the surface area of the synthesized MWCNTs was investigated, the surface area decreased as the temperature increased. The prepared CNTs were purified using chemical oxidation method and the effect of acid treatment on CNTs surface was examined by TEM and SEM. The function groups produced at CNTs surface were investigated by using FTIR spectroscopy also the effect of CNTs preparation temperature on FTIR spectra was studied. The functionalized CNTs were used for adsorption of some heavy metals and for removal of some organic dyes from water.     

一些含三氮杂茂偶氮染料O,N供体的Zr（Ⅱ）配合物的合成、表征和抗微生物活性

合成了9种3-（2-羟基萘基-1-偶氮）-1,2,4-三氮唑（HL¹）,3-（2,4-二羟苯基-1-偶氮）-1,2,4-三氮唑（HL²）,3-（2-羟基-3-羧基萘基-1-偶氮）-1,2,4-三氮唑（HL³）,3-（2-羟基-5-溴苯基-1-偶氮）-1,2,4-三氮唑（HL⁴）和3-（2-羟基-5-甲基苯基-1-偶氮）-1,2,4-1,2,4-三氮唑（HL⁵）的Zr(Ⅱ)配合物并用元素分析,摩尔电导,磁矩,IR,UV-Vis,¹H-NMR以及热分析（TGA和DTA）对其进行了表征。结果表明HL¹-HL⁵以二齿一元配体方式通过偶氮的氮原子和羟基基团的氧原子与Zr(Ⅱ)离子配位生成单核配合物。用4种革兰氏阴性菌,即大肠杆菌（Escherichia coli）,粘质沙雷氏菌（Serratia marcescens）,阴沟肠杆菌（Enterobacter cloacae）和普通变形杆菌（Proteus vulgaris）,以及2种真菌,即白色念珠菌（Candida albicans）和黑曲霉菌（Aspergillus niger）对配体及其配合物的生物学活性进行了研究。最小抑菌浓度（MICs）用纸上杯碟琼脂扩散法测定,结果表明在大多数情况下,金属化的配合物的抗微生物活性与自由配体相比有所增强。     

Kinetics and mechanisms of the reduction of Cu0.5Zn0.5Fe2O4 with hydrogen at 400–600 °C for the production of metallic nanoparticles

Ferrites have continued to attract attention over years. As magnetic materials, ferrites cannot be replaced by any other magnetic material because they are relatively inexpensive, stable and have a wide range of technological applications in transformer core, high quality filters, high frequency circuits and operating devices. Nanocrystallite sizes of Cu_0.5 Zn_0.5Fe₂O₄ with 25 nm have been obtained by hydrothermal route. Cu_0.5Zn_0.5Fe₂O₄ powder was isothermally reduced in H₂ flow at 400–600 °C. The reduction behavior of the produced powder as well as the influence of reduction temperature on the structural characteristics of the products was extensively studied. Microstructure of partially and completely reduced samples was investigated and the activation energy values were calculated from Arrhenius equation. The activation energy for nanocrystallite Cu_0.5 Zn_0.5Fe₂O₄ reduced at the initial stage was found to be 37.4 kJ/mole, while that at the final stage is 14 kJ/mole. The approved mathematical formulations for the different crystallite sizes gas solid reaction were applied and it was found that at the final stages the reaction is controlled by the gaseous diffusion while the combined gaseous diffusion and interfacial chemical reaction is the rate controlling mechanisms at the initial stages. The reduction process produce nanoparticles metallic phases of iron, copper and zinc, which have ball and fibers shapes.