Facile Route Using Highly Arrayed PMMA Spheres as Hard Template for the Fabrication of 3D Ordered Nanoporous MgO

"Using magnesium nitrate as Mg source and regularly packed polymethyl methacrylate (PMMA) spheres were synthesized via a combined strategy of emulsifier-free emulsion polymerization and water floating technique as hard template, we fabricated ordered nanoporous magnesium oxide. The synthesized PMMA and MgO samples were characterized by N2 adsorption-desorption, X-ray diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. It was observed that the synthesized PMMA spheres possessed a uniform diameter of approximately 284 nm and were in a highly ordered array, and the MgO generated by using the PMMA-templating method exhibited polycrystallinity with three-dimensionally ordered pores. BET surface area of the synthesized MgO sample is 100.7 m2/g, pore volume is 0.46 cm3/g, wall thickness is 4-24 nm, and pore sizes are in the range of 10-120 nm. Such a 3D high-surface-area nanoporous strongly basic MgO is useful in the applications of catalyst supports and acidic gas adsorbents."     

Mechanism of stress cracking of poly(ethylene terephthalate) beverage bottles: A method for the prevention of stress cracking based on water hardness

A recently described bottle test method was used to evaluate the dependence of stress crack failure of poly(ethylene terephthalate) (PET) carbonated soft drink bottles on water hardness. Although the industry belief is that water hardness is irrelevant to stress cracking, it was found that hardness ions exert a tremendous positive impact by deactivating water alkalinity through precipitation as harmless carbonate minerals. This mitigating effect of hardness means that no complete understanding of stress cracking as a function of alkalinity is possible without also considering water hardness. A useful concept is that of excess alkalinity, which is defined as alkalinity that is not precipitated during solution evaporation. Limiting excess alkalinity by using water with sufficient hardness is an effective means of stress crack prevention in PET soft drink bottles. Evaluation of compositions which are typical of those used for lubricating PET bottles on production conveyors showed that the role of these compositions in stress cracking was that of spectators, that is, they neither cause failure if water does not otherwise cause it, nor stop failure if water otherwise causes it.     

A novel method of determining hard-core radius and roughness factor for organic mixtures

The translational–rotational coupling factor or the roughness factor coefficient introduced by Chandler has been evaluated for a number of organic mixtures containing hydrocarbons from their shear viscosity. The hard-core radius and hence the radial distribution function at contact, required in such an evaluation is obtained through a novel method. Its variation with temperature and concentration is discussed. With the available shear viscosity measurements, the roughness factor is also calculated and analyzed.     

Comparison of the effects of visible femtosecond laser pulses and continuous wave laser radiation of low average intensity on the clonogenicity of Escherichia coli.

To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (λ = 620 nm, τ_p=3 × 10⁻¹³ s, f_p = 0.5 Hz, E_p = 1.1 × 10⁻³J cm⁻², I_av = 5.5 × 10⁻⁴ W cm⁻², I_p = 10⁹ W cm⁻²) and continuous wave (CW) laser radiation (λ = 632.8 nm, I = 1.3 W cm⁻²). The irradiation dose required to produce a similar biological effect (a 160%–190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 10³ lower for pulsed radiation than for CW radiation (3.3 × 10⁻¹ and 7.8 × 10² J cm⁻² respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 Å, which corresponds to the size of the chromophores of hypothetical primary photoacceptors—respiratory chain components.     

Comparison of the effects of visible femtosecond laser pulses and continuous wave laser radiation of low average intensity on the clonogenicity of Escherichia coli

To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (λ = 620 nm, τ_p=3 × 10⁻¹³ s, f_p = 0.5 Hz, E_p = 1.1 × 10⁻³J cm⁻², I_av = 5.5 × 10⁻⁴ W cm⁻², I_p = 10⁹ W cm⁻²) and continuous wave (CW) laser radiation (λ = 632.8 nm, I = 1.3 W cm⁻²). The irradiation dose required to produce a similar biological effect (a 160%–190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 10³ lower for pulsed radiation than for CW radiation (3.3 × 10⁻¹ and 7.8 × 10² J cm⁻² respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 Å, which corresponds to the size of the chromophores of hypothetical primary photoacceptors—respiratory chain components.     

Rapid and simple method for measuring the linearity of sucrose gradients

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On the investigation of nitroparaffins by conversion into hydroxamic acidsII. Determination of primary nitroparaffins

Teil I: siehe [4]     

The micellar behavior of linear triblock terpolymers of styrene (S), isoprene (I), and methyl methacrylate (MMA) in selective solvents for PS and PMMA

A series of linear triblock terpolymers consisting of polystyrene (PS), polyisoprene (PI) and poly(methyl methacrylate) (PMMA) were examined in tetrahydrofuran (THF), a good solvent for all the blocks and in dimethylacetamide (DMA) and dimethylformamide (DMF), selective solvents for PS and PMMA. In DMA and DMF, which are both non-solvents for PI, multimolecular micelles were formed. The micelles were characterized by low-angle laser light scattering (LALLS), dynamic light scattering (DLS) and viscometry. The aggregation number of the triblock terpolymers was greater in DMF than in DMA, reflecting the higher non-solvent strength of DMF for PI. The aggregation number was also found to increase with increasing PI content of the terpolymers in both DMA and DMF. The hydrodynamic radii depended on the aggregation number of the micelle and the length of the corona forming PS and PMMA blocks. The complexity involved in studying a system consisting of three different polymer blocks is discussed in the context of the results obtained.     

Fatigue behavior of polystyrene (PS) analyzed from the Fourier transform (FT) of stress response: First evidence of I2/1(N) and I3/1(N) as new fingerprints

The fatigue behavior of polystyrene (PS) in strain controlled torsion rectangular oscillatory tests was analyzed via Fourier transform (FT) to better understand the time evolution of linear and nonlinear mechanical parameters, and to establish fingerprints related to failure onset. The tests were performed under large amplitude oscillatory shear (LAOS), so the stress response was no longer perfectly sinusoidal and higher harmonics could be detected and quantified in the FT spectra as a function of time or number of cycles N. A linear parameter, the storage modulus (G′(N)), was analyzed, as well as nonlinear parameters of the ratios of the second (I₂(N)) and the third (I₃(N)) harmonics over the fundamental one (I₁(N)). The nonlinear parameter I_2/1(N) is very low for undamaged samples, but its intensity was found to increase when defects were created in the structure to a point where cracks became visible in the sample. On the other hand, the I_3/1(N) parameter increased steadily during a test up to a local maximum where a macroscopic crack occurs in the sample. Both parameters I_2/1(N) and I_3/1(N) are proposed as new criteria to detect the onset of part failure under the conditions tested and can be used as safety limits for partial damage.     

On the accuracy of correlation energy calculated by the correlation factor method: first- and second-row atoms

Summary The correlation energy of two- and four-isoelectronic series, a representative example for which the existing spin-density functionals fails, is calculated using the Colle and Salvetti method, considering mono- and multideterminantal wave functions. The results are in agreement with experimental data, and show the potentiality of this method when it is applied to wave functions including the most relevant configurational features. Also, results for the ionization energies and electron affinities of first- and second-row atoms are reported.     

Oxidation of ultra high molecular weight polyethylene (UHMWPE) part 2: Critical examination of the total luminescence intensity (TLI) method for determining hydroperoxides

The validity of the total luminescence intensity (TLI) method for determining the amount of hydroperoxides in a UHMWPE sample has been assessed. Measurements of hydroperoxides with FTIR before and after a TLI run showed that only about 50% of the hydroperoxides were decomposed at 150 °C. It was also found that this value was not constant with ageing time, which means that the TLI value could not be representative of the total number of hydroperoxides in a sample as a function of ageing time. Thermoluminescence was also found to complicate the measurements and could, if care was not taken, give TLI values that were much too high. In addition it was found that the TLI value is actually connected with the build-up of carbonyls rather than the build-up of hydroperoxides. This last finding is consistent with part one of this study, where it was reported that CL from oxidising UHMWPE is a type of activated CL, where carbonyls are the activating species. From all of these results it is concluded that TLI is not a suitable method for determining hydroperoxides in UHMWPE.     

Evaluation of robustness to surface conditions of the target factor analysis method for determining the dielectric function from reflection electron energy loss spectra: Application to GaAs

Target factor analysis (TFA) of a series of angle‐resolved reflection electron energy loss spectra (REELS) was recently demonstrated to be a useful method to determine bulk energy loss functions (ELFs), which by the TFA are separated from the surface‐loss structures of REELS. The dielectric function is then readily derived by Kramers–Kronig analysis of the ELF. The advantage of the method compared with other methods, which are also based on the analysis of REELS, is that the condition of the outermost surface region is unimportant because the excitations that occur there are removed by the TFA and ideally a pure bulk component is determined. Our method is thus particularly useful for determining the ELF from compound materials that are hard to clean without modifying the outermost atomic layers. In this paper, the robustness of the method was studied by applying it to three GaAs samples with different surface compositions caused by different surface cleaning methods. The results showed that when electrons of energy 3000–4500 eV were used, the resulting bulk ELFs were essentially identical except for small differences for the sample that had the largest thickness of the modified surface layer. It is concluded that this is a useful method, provided that the thickness of the modified layer is kept to a minimum by using shallow angle sputtering and by using REELS electrons at a sufficiently high energy that a major part of the electron trajectories are at a depth larger than the thickness of the modified surface layer. Copyright © 2013 John Wiley & Sons, Ltd.     

Combination of the ionic-to-atomic line intensity ratios from two test elements for the diagnostic of plasma temperature and electron number density in Inductively Coupled Plasma Atomic Emission Spectroscopy

In Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) spectrochemical analysis, the MgII(280.270 nm)/MgI(285.213 nm) ionic to atomic line intensity ratio is commonly used as a monitor of the robustness of operating conditions. This approach is based on the univocal relationship existing between intensity ratio and plasma temperature, for a pure argon atmospheric ICP in thermodynamic equilibrium. In a multi-elemental plasma in the lower temperature range, the measurement of the intensity ratio may not be sufficient to characterize temperature and electron density. In such a range, the correct relationship between intensity ratio and plasma temperature can be calculated only when the complete plasma composition is known. We propose the combination of the line intensity ratios of two test elements (double ratio) as an effective diagnostic tool for a multi-elemental low temperature LTE plasma of unknown composition. In particular, the variation of the double ratio allows us discriminating changes in the plasma temperature from changes in the electron density. Thus, the effects on plasma excitation and ionization possibly caused by introduction of different samples and matrices in non-robust conditions can be more accurately interpreted. The method is illustrated by the measurement of plasma temperature and electron density in a specific analytic case.     

Comparison of the possibilities of gas chromatography-mass spectrometry and tandem mass spectrometry systems for the analysis of anabolics in biological material

Chromatographic techniques such as GC-MS play a most important role in modern multi-residue analysis of anabolic steroids. The major difference between GC-MS apparatus from different manufacturers is the way of detection and recording. Most apparatus use selected-ion monitoring (SIM) for the determination of low concentrations. Systems based on ion trap technology record in full-scan to even picogram concentrations using a computer algorithm to compare the most important peaks of the mass spectrum of the unknown to those of the standard.

In this investigation the possibilities of ion trap GC-MS and the recently released GCQ MS and MS₂ for the analysis of anabolics in biological material are compared.     

Evaluation of the parameters of the Bender equation of state for low acentric factor fluids and carbon dioxide

Volumetric properties of several low acentric factor fluids (Ar, CH₄, C₂H₆, Kr, N₂, Ne, O₂, Xe) as well as CO₂ are modeled using the Bender equation of state. This equation is a linear function of 19 adjustable parameters, which are evaluated from properties data, using a linear numerical procedure. The validity of the EOS is tested by calculating the Joule-Thomson inversion curve. A simple model is in particular used to correlate the inversion properties predicted by the Bender equation, expressed in term of reduced pressure as a function of reduced temperatures ranging from 0.8 to 6. The simple correlation reproduces accurately the used data. We employ data on state behaviour ρ(P,T) of homogeneous fluid phases, vapour-liquid equilibrium, second virial coefficient and the coordinates of the critical point.     

The s-homodesmotic method for the computation of conventional strain energies of bicyclic systems and individual rings within these systems

The s-homodesmotic method for computing conventional strain energies (CSE) has been extended for the first time to bicyclic systems and to individual rings within these systems. Unique isodesmic, homodesmotic, and hyperhomodesmotic reactions originate from the s-homodesmotic method. These are used to investigate 12 bicyclic systems comprising cyclopropane and cyclobutane and how the CSE of each system compares to the sum of the individual rings within each. Equilibrium geometries, harmonic vibrational frequencies, and the corresponding electronic energies and zero point vibrational energy corrections are computed for all relevant molecules using second-order perturbation theory and density functional theory (B3LYP) with the correlation consistent basis sets cc-pVDZ and cc-pVTZ. Single-point CCSD(T) energies are computed at the MP2/cc-pVTZ optimized geometries to ascertain the importance of higher order correlation effects. Results indicate that CSEs are additive when the two rings are separated by one or two bonds and somewhat additive in other cases.     

Radial and longitudinal profiles of the electron paramagnetic resonance signal intensity of a single TE102 rectangular cavity: A three-dimensional surface plot for a point-like sample

Radial and longitudinal profiles of the electron paramagnetic resonance (EPR) signal intensity of a point-like sample inserted into a Bruker single TE₁₀₂ rectangular cavity were computed and the three-dimensional surface plots presented for the set of the point-like samples situated, (i) at any available points, P(ρ∈〈0, b/2〉, φ∈〈0, 2π〉, x=0), of a circle with a radius, ρ_max=b/2 (5.5 mm), which is located in the horizontal, central (y-z)-plane of the microwave cavity (a radial profile), and (ii) at any available points, P(ρ=b/4, φ∈〈0, 2π〉, x∈〈−a/2, a/2〉), of the cylindrical surface with a radius, ρ=b/4, and length, L=a (23.5 mm), which is concentric with the vertical, central x-axis of the microwave cavity (a longitudinal profile). The three-dimensional surface plots of the EPR signal intensity can be used for the theoretical prediction of the experimental response of the microwave cavity to a bulky sample: (i) for movement along (the longitudinal response); and (ii) for rotation around (the radial response) the vertical, central cavity x-axis.