Studies of porous polymer gels. I. One-step suspension technique for preparation of moderately crosslinked methacrylic acid gels

A new method of preparation of carboxyl cation exchangers directly from methacrylic acid and divinylbenzene is described. A suspension technique with a concentrated aqueous calcium chloride solution as the water phase was used. n-Octane and toluene were inert diluents of the monomers. The copolymers obtained have high ion-exchange capacity (9.6–10.6 mequ./g) and porous structure.     

The age of cows as a factor shaping the antioxidant level during a nutritional experiment with fish oil and linseed supplementation for increasing the antioxidant value of milk

BACKGROUND: So far, in research studies, the age of cows has not been considered as a factor that may influence the changes in the content of milk ingredients with antioxidant properties modified by the feed supplementation. The aim of this study was to determine the influence of supplementation on the content of ingredients having antioxidant properties and to determine the influence of the age of cows taking part in the experiment on these changes. The experiment was conducted using 20 Polish Holstein Friesian cows, 10 primiparous and 10 multiparous. The combined supplementation of fish oil and linseed constituted the experimental factor. RESULTS: The milk of primiparous cows after 21 days of supplementation was characterised by a higher content of C18:1 trans ‐11, C18:2 cis ‐9, trans ‐11, α‐retinol, α‐tocopherol and β‐lactoglobulin compared to the milk of multiparous cows, in which a higher level of lactoferrin, C20:5 and β‐carotene was recorded. In both groups an increase in the total antioxidant status was noted (a higher level in the milk of primiparous cows). CONCLUSIONS: Modification of the diet of cows with fish oil and linseed significantly influenced antioxidant properties of their milk; however, the response of multiparous and primaparous cows was noticeably different to the supplement introduced. Copyright © 2012 Society of Chemical Industry     

Differentiation of raw spirits of rye, corn and potato using chromatographic profiles of volatile compounds

BACKGROUND: The origin of the raw spirits influences the sensory quality of rectified spirits that are subsequently used for the production of vodka. The aim of this research was to evaluate the effectiveness of two methods based on the comparison of profiles of volatile compounds [solid phase microextraction–gas chromatography–mass spectrometry (SPME‐GC‐MS) and gas chromatography with flame ionisation detection (GC‐FID)] for the determination of origin of raw spirits obtained from rye, corn (maize) and potato. RESULTS: Profiles obtained for the volatile compounds by using these methods were different and were influenced by the sample introduction method. The main groups of volatiles obtained using SPME‐GC‐MS method were fatty acid ethyl esters, while in the case of GC‐FID fusel alcohols and ethyl acetate dominated. Data obtained from these methods were treated using principal component analysis and linear discriminant analysis to test the possibility of sample differentiation and classification. It was relatively easy to differentiate potato spirits from the remainder; however, it was not possible to fully distinguish the corn samples from rye samples. The classification ability of the SPME‐GC‐MS method was 95% but the prediction ability was 97.4%. For the GC‐FID method the classification ability was 90.1%, whereas the prediction ability was 94.27%. CONCLUSIONS: The methods presented can be used for reliable differentiation of potato spirits from corn and rye spirits. Copyright © 2012 Society of Chemical Industry     

Air-gaps in 0.3 /spl mu/m electrical interconnections

A copper/air-gap interconnection structure using a sacrificial polymer and SiO/sub 2/ in a damascene process has been demonstrated. The air-gap occupies the entire intralevel volume with fully densified SiO/sub 2/ as the planar interlevel dielectric. The copper was deposited by physical vapor deposition and planarized by chemical-mechanical planarization. The Ta/Cu barrier/seed layer was deposited by physical vapor deposition; the bulk copper was electrochemically deposited. The resulting structure has an effective intralevel dielectric constant of 2.19.     

Microscopic Charge Inhomogeneities in Underdoped La2−xSrxCuO4: Local Structural Evidence

We present local structural evidence for the existence of charge inhomogeneities at low temperature in underdoped and optimally doped La_2?x Sr _x CuO₄. The inhomogeneities disappear for x ≥ 0.2. The evidence for the charge inhomogeneities comes from an anomalous increase in the inplane Cu–O bond length distribution in the underdoped samples as well as evidence for CuO₆ octahedral tilt inhomogeneities in the intermediate range structure. Preliminary analysis of the temperature dependence of this phenomenon indicates that the inhomogeneities set in at temperatures in the range 60 K < T _co < 130 K, which depends on doping.     

Vibrational spectroscopy and periodic DFT studies of LaMg2PdH7: A material with two types of hydride

The need for a safe, reliable and cheap method for hydrogen transportation has prompted an intense effort in the synthesis of novel hydrides. To direct the search for better materials, it is essential to understand the bonding present in these systems. A newly synthesized material is LaMg₂PdH₇ which is best formulated as {La³⁺}{Mg²⁺}₂{[PdH₄]⁴⁻}{H⁻}₃. Thus hydrogen is formally present both as a free hydride ion and also as a covalently bound ligand. The combination of inelastic neutron scattering (INS), infrared and Raman spectroscopies and periodic density functional theory (DFT) has been used to characterise the material. We find that the material is less ionic than Ba₂[PdH₄], which also contains [PdH₄]⁴⁻. The charges carried by both the coordinating and free hydrides are similar which hints at a degree of covalency in the interactions between the interstitial hydrides and the lanthanum and magnesium ions.     

Novel approach for measuring the effective shear modulus of porous materials

A new approach is proposed for the experimental study of the effective shear modulus of porous elastic materials using the uniaxial tension test. The idea is to measure strains at a few points surrounding a cluster of holes that represents the structure of the material. The representative cluster is placed in the material with the same elastic properties as those of the matrix. The measured strains lead to the properties of the equivalent circular inhomogeneity, which would produce the same elastic fields as from the cluster. An aluminum plate containing a cluster of seven circular or hexagonal holes was used. The effective shear modulus obtained from the strain data was compared with theoretical predictions and various bounds, and it was shown that the laboratory estimated values are quite accurate. The experimental technique can be used for the determination of the effective Poisson’s ratio of porous media and/or cellular solids if more detailed strain data are obtained.     

Study of spray cooling of a pressure vessel head of a boiling water reactor

The present paper deals with a theoretical analysis of the spray cooling of a Reactor Pressure Vessel (RPV) head in a Boiling Water Reactor (BWR). To this end a detailed computational model has been developed. The model predicts the trajectories, diameters and temperatures of subcooled droplets moving in saturated vapor. The model has been validated through comparison with experimental data, in which droplet temperatures were measured as functions of the distance that they cover in saturated vapor from the moment they leave the sprinkler outlet to the moment they impact on the RPV head inner wall. The calculations are in very good agreement with measurements, confirming the model adequacy for the present study. The model has been used for a parametric study to investigate the influence of several parameters on the cooling efficiency of the spray system. Based on the study it has been shown that one of the main parameters that govern the temperature increase in a subcooled droplet is its initial diameter. Comparisons are also made between conclusions from the theoretical model and observations made through flow and temperature measurements in the plant (Forsmark 1 and 2). One of these observations is that the rate at which the RPV head temperature decreases on the way down from hot to cold standby is constant and independent of the sprinkling flow rate as long as the flow rate is above a certain minimum value. Accordingly, the theoretical model shows that if one assumes that the cooling of the RPV head is through a water film built on the inner wall due to sprinkling, the heat removal rate is only very weakly dependent on the sprinkling flow rate.     

一种新的鲁棒自适应控制律

本文提出了一神新的称为θ-δ修正法的鲁棒自适应控制律.与其它修正法比较,θ-δ修 正法不会使系统性能退化.即在无摄动的理想情况下,这种自适应律可以保证跟踪误差以及 自适应回路里的其它信号为渐近稳定.当系统受到摄动时,该自适应律是鲁棒的且无论设计 常数γ是大是小,输出误差的漂移都很小,因而γ可以取大于零的任意值.